Why is my iMac with Big Sur not seeing wifi networks?

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Level 1

39 points

Why is my iMac with Big Sur not seeing wifi networks?

Today, my iMac with Big Sur 11.1 decided it would not connect to our wifi networks. So I turned wifi off, and then on again, to see if that resolved the issue. Nope. Now I can't even turn wifi on. If I go to System Prefs and click the wifi switch, nothing happens. It stays switched off. None of my networks are listed, and the wifi icon on the menu bar is greyed-out and has a slash through it.

I am now running an ethernet cable direct to the modem to maintain a connection. All of my other devices (iPhones, iPads, MacBook, TV, Playstation etc) can connect fine, there is no disruption, only the iMac.

Here's what I have tried so far:

Rebooted computer
Rebooted modem
Rebooted routers (I have multiple wifi networks in parallel but none are visible)
Deleted plist files from system preferences folder and restarted
Created a new wifi configuration in System Prefs
Reinstalled a clean version of BigSur

None of these have resolved the issue or changed the symptoms. Curiously, the wifi switch on my menu bar is ON, but with no networks displayed. In System Prefs, wifi is OFF, and can't be switched on.

Help??

iMac 27″ 5K, macOS 11.1

Posted on Jan 19, 2021 2:12 AM

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Answer 1

Top-ranking reply

Matti Haveri

Level 6

19,808 points

Jan 19, 2021 3:20 AM in response to Jamie Crain

Maybe the WiFi module is broken. What does the System HW report say about it? Unlikely that this is Big Sur related but it would be interesting to check whether a clean Mojave (or Catalina) install on an external disk has the same error after SMC and PRAM reset.

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Answer 2

Jamie Crain Author

Level 1

39 points

Jan 31, 2021 9:09 PM in response to Jamie Crain

Hi All

I have resolved this issue. Here's what happened (explanations welcome because I don't understand what happened).

I contacted Apple Support who put me in touch with a local Apple repairer. The repairer wouldn't comment on the symptoms until they had seen the machine in person, but as it was inconvenient getting there, I did not get to show them the iMac.

Instead, I ordered a USB Wi-fi Adapter like this one here:

https://www.amazon.com.au/gp/product/B07YBS7C4R/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

It arrived today so I plugged it in. Suddenly, the wi-fi icon in the menu bar came back to life. I thought, "Wow that's great, so easy to set up, didn't even need a driver."

Then I realised - it wasn't set up. The wi-fi was actually using the built-in wi-fi card from the iMac. Somehow, merely plugging in the USB Adapter triggered the machine to fix itself!

The only thing that is different, is that now there is a "Hidden network" warning message, that wasn't there previously.

So it seems it was a Mac OS software bug after all...now I just need to decide whether to send the Adapter back, or hang on to it in case the iMac loses the wifi again. If anyone can explain why the iMac would behave like this, I'd love to know.

Thanks everyone.

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Answer 3

Old Toad

Level 10

215,784 points

Jan 19, 2021 1:38 PM in response to Jamie Crain

Boot into Safe Mode by booting with the Shift key held down and check there to see if the problem persists. Reboot normally and test again.

NOTE: Safe Mode boot can take up to 10 minutes as it's doing the following;

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts

• Deletes font caches, kernel cache, and other system cache files

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Answer 4

Jan 19, 2021 2:51 AM in response to Jamie Crain

Any poorly shielded USB devices nearby? I have one such USB device that blocks both wifi and bluetooth when it is used.

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Answer 5

Owl-53

Level 10

103,159 points

Jan 19, 2021 2:23 AM in response to Jamie Crain

Reset the SMC or Reset the NVRAM or try booting into and new Test Account with Admin Privileges, does it occur there also ?

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Answer 6

Owl-53

Level 10

103,159 points

Jan 20, 2021 3:38 AM in response to Jamie Crain

One could try the Etrecheck in Full Disk Access - free and from a Very reliable Apple Community Poster and Developer. Will give a complete look at the system and if malware present, will offer to remove it. The App does not reveal and personal details just hardware and software snapshot

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Answer 7

Old Toad

Level 10

215,784 points

Jan 21, 2021 11:26 AM in response to Jamie Crain

There are other things that we look for in the report. Post it in your replay as follows:

Copy the report

and use the Additional Text button to include the report in your reply.

IMPORTANT:

Before running Etrecheck assign Full Disk Access to Etrecheck in the Etrecheck's Privacy preference pane so that it can get additional information from the Console and log files for the report:

Also click and read the About info to further permit full disk access.

Then we can examine the report and see if we can determine what might be causing the problem.

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Answer 8

Old Toad

Level 10

215,784 points

Jan 21, 2021 3:18 PM in response to Jamie Crain

There is no reason to ever install or run any 3rd party "cleaning", "optimizing", "speed-up", anti-virus, VPN or security apps on your Mac. This user tip describes what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community

That being said you should uninstall CleanerOnePro according to the developer's instructions.

Next, go into the System/Network preference pane and move WiFi to the top of the sidebar as shown in this screenshot:

by using this menu:

It appears that you have it setup as shown above and WiFi should be at the top of the sidebar

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Answer 9

Old Toad

Level 10

215,784 points

Jan 22, 2021 9:25 AM in response to redhead101

Show me where Jamie said he had already:

1 - booted into Safe Mode

2 - ran Etrecheck

3 - another ethernet cable

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Answer 10

Jamie Crain Author

Level 1

39 points

Jan 19, 2021 2:54 AM in response to Matti Haveri

All unplugged.

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Answer 11

Jamie Crain Author

Level 1

39 points

Jan 19, 2021 3:08 AM in response to Jamie Crain

I should also point out that prior to this happening (total wifi failure), I noticed that the wifi was disconnecting fairly frequently and 'hunting' for the network before reconnecting. I would watch this happen on the screen, yet on my iPhone the wifi connection on the same network would never miss a beat. The same thing was happening to my wife's MacBook Air in a different room, but at different times.

This only happened after we upgraded to Big Sur, but of course that could be a red herring.

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Answer 12

Jamie Crain Author

Level 1

39 points

Jan 19, 2021 2:02 PM in response to Old Toad

THanks, yes I have tried Safe Mode previously and nothing changed. Will try again.

Second attempt: No change. (BTW - Running the computer in Safe Mode is very slow. Everything is laggy)

Is it possible I have some sort of Malware/Virus that is causing this issue with wifi? Big Sur certainly has a few quirks but I haven't noticed anything else.

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Answer 13

Jamie Crain Author

Level 1

39 points

Jan 21, 2021 3:39 PM in response to Old Toad

Thanks for the tip re 3rd party apps. I usually used COPro for keeping an eye on memory usage or for finding big files. Now deleted.

I have set the wi-fi as top in the Service Order box, but it won't remain there when I click OK. On the main pane, it stays exactly where it is, below Bluetooth and Ethernet. I have tried various orders and I've observed that I can get Wi-fi to move above Thunderbolt, and vice versa, but nothing else changes no matter what I do.

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Answer 14

Jan 21, 2021 7:27 PM in response to Old Toad

Old Toad You just keep telling Jamie Crain to just do things he has already done on his iMac to try to get WiFi to turn back on and to just connect to his own private internet connection afterwards and non of what you have suggested so far is working for him at all.

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Answer 15

Jamie Crain Author

Level 1

39 points

Jan 24, 2021 6:09 PM in response to Old Toad

Thanks everyone. On the rare occasion that I can't fix my own issues I come to the discussions forum where I am grateful to receive tips from people all over the world. I appreciate the time people donate and I am willing to try any sensible idea.

Unfortunately on this occasion I have drawn a blank and the issue remains unresolved. I will contact Apple and see if they can assist.

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Why is my iMac with Big Sur not seeing wifi networks?

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