After upgrading to macOS Catalina, my Macbook Pro no longer detects external displays. I've tried three different external display models, all Samsung branded (S27E591C, C27F398, C32F391). I've tried different HDMI to USB-C cables. I reset the SMC per an article I read that recommended doing so, but that did not solve the problem. Any other troubleshooting ideas would be greatly appreciated.
Hey Alex! Thanks for the help. I am not 100% certain resetting the NVRAM solved the problem, but I'm going to go ahead and mark that it did. In a nutshell, here are the steps I performed in order to get the external displays to work:
(1) Reset the NVRAM with the external monitor plugged in via USB-C to HDMI cable
(2) Updated to macOS Catalina 10.15
(3) Waited for ~10 minutes, the external monitor's screen flashed, and suddenly started working
Fun fact: I plugged in a second external monitor, and macOS Catalina did not detect the new display right away. Again, I had to wait for ~10 minutes before the screen flashed and the display was detected. Very odd, but alas, both my external displays are working now.
Thanks for the help!
Hey Alex! Thanks for the help. I am not 100% certain resetting the NVRAM solved the problem, but I'm going to go ahead and mark that it did. In a nutshell, here are the steps I performed in order to get the external displays to work:
(1) Reset the NVRAM with the external monitor plugged in via USB-C to HDMI cable
(2) Updated to macOS Catalina 10.15
(3) Waited for ~10 minutes, the external monitor's screen flashed, and suddenly started working
Fun fact: I plugged in a second external monitor, and macOS Catalina did not detect the new display right away. Again, I had to wait for ~10 minutes before the screen flashed and the display was detected. Very odd, but alas, both my external displays are working now.
Thanks for the help!
SOLVED!
At my office, some Mac users (myself included) had the Catalina display problem and some didn't. Turns out it has to do with the type of connector. Those with an HDMI connection were OK, and those without were not. So we experimented with different cables to see when the external display connects:
So for us the secret is to replace your cable to one that includes HDMI at some point. I got a DVI-to-HDMI cable, then used a dongle that converts HDMI-to-USBC. Works fine now!
Everybody—the "correct" answer is actually not what solved my problem in the end. I had to replace the USB-C to HDMI cables I was using with both my external monitors. The cables I was using did not support 60Hz. The new cables I purchased did.
My recommendation for anybody who is continuing to have this problem after resetting their NVRAM/PRAM is to purchase (or better yet borrow to test) a new cable that supports 60hz to see if that solves your problem.
Note: It should be noted this is STILL a software issue that Apple should be able to resolve in a patch, but for those of you who cannot wait I'd recommend the my solution above.
to get a Mac display to become active, you need the Mac to query the display, and the display to answer with its name and capabilities. Otherwise, the display will not be shown as present, and no data will be sent to the display.
This query is only sent at certain times:
• at startup
• at wake from sleep
• at insertion of the Mac-end of the display-cable, provided everything on that cable is ready-to-go
• on invoking Option-(Detect Display) button in Displays preferences
For a MacBook Pro that has a working built-in display, the obvious choice is the Last one -- to hold the Option key in Displays preferences and look for the appearance of the (Detect Displays) Button and click on it.
For what it's worth, I purchased a new HDMI to USB-C cable, 4K / 60Hz, in an attempt to troubleshoot this issue. The Macbook Pro instantly recognized the external display when using the new cable.
The HDMI to USB-C cable I used previously was 4K / 30Hz.
I would bet the 60Hz vs 30Hz variable is related to this issue. My 30Hz cables used to work perfectly prior to Catalina, so this is likely a software (driver) issue Apple can resolve in a future patch.
I am pretty sure this is an issue with HDMI and Catalina. When using my two external monitors with USB-C to HDMI leads it takes ages for them to be recognised (30 mins or more). I switched them for USB-C to DVI cables and the monitors are recognised instantly.
Ended up using the adapter below and now no issues with sleep or start up. Full resolution. Much better than HDMI resolution and no VGA adapter issues as before. This adapts the OEM dell cable to the Mac.
USB C to DisplayPort Cable,QGeeM 4K@60HZ Thunderbolt 3 to DP Adapter Compatible with MacBook Pro 2019/2018,ipad pro 2018,Surface Book,Dell XPS,Sumsang Galaxy S10 Note 9 Dex,USB C to DP Adapter https://www.amazon.com/dp/B07YDNSGY2/ref=cm_sw_r_cp_api_i_OBP9DbFAHM104
Our office displays are not 4k so it may not apply to those with 4k. But for those of us with older monitors (mine's 1080x1920), changing from DVI-to-USBC to DVI-to-HDMI-to-USBC did the trick. Just letting folks know that a connector change brought displays back online for several users in my office (we all tried the NVRAM and SCM resets first). I hope this helps someone else.
The answer to this is here:
https://discussions.apple.com/thread/250729389?answerId=252101885022#252101885022
Basically, you probably have cables that are only 30hz. Catalina somehow breaks 30hz cables and 60 hz cables work.
This solved the problem for me. Dell 4k monitor on MacBookPro, no longer recognized after Catalina. Resetting the NVRAM worked immediately. Thanks!
I also had this problem. I have a 2017 iMac and have a dell external second display. After reading hundreds of post and trying all of the listed remedies, nothing. It happened the first time on Catalina 10.15.1, reset things and it reappeared. With the release of 10.15.2, display not recognized. Tried everything to no avail. Finally read a post that said to simply unplug the power from your external display for an hour. I did this and plugged it back it and much to my surprise, it works! I’m not sure if the display has to reset or what but it works.
This thread seems to indicate that the bulk of the issues are HDMI related: https://discussions.apple.com/thread/250715830
Whatever the case it is defo a software issue IMHO. I am glad that the USB-C to DVI cables saved the day for me but I am rather irked at having to purchase something just to work around a buggy software upgrade.
JJ512--
If you had display connected to an external box via regular USB cables, then to your display using legacy protocol such as HDMI or DVI or VGA, you were likely using DisplayLink technology.
Visit DisplayLink.com and get updated software for Catalina, because Catalina will not be able to load the old Driver.
Hello bkuyah!
Thanks for reaching out to the Apple Support Communities. I understand that you’re having difficulty connecting your MacBook Pro to external displays. You’ve done a great job testing out different displays, as well as HDMI to USB-C cables and resetting the SMC.
The next step will be to follow the steps in this article for the appropriate issue which is occurring: Get help with video issues on external displays connected to your Mac.
Enjoy the day!
I have a MacBook Pro (13-inch, 2017, Two Thunderbolt 3 ports) for work and have been having the same issues. I have a UPTAB USB-C adapter for my Apple Cinema Display that has been working for over a year until the recent macOS Catalina update. Also purchased ITD ITANDA USB-C adapter and it does not work as well. The IT department at my work tried resetting the NVRAM and SMC to no avail. They determined that it is indeed the the macOS Catalina software that is not recognizing the adapter. We have a second same model computer still using macOS Mojave and the UpTab C-Type adapter works fine. I also reached out to UPTAB tech support and have not heard back. IT indicated that they might have to uninstall Catalina and go back to Mojave to fix the problem. Is there ever going to be an update from Apple to fix this problem so I don't have to use Mojave? Is there anything else I can do to resolve this issue? Any help would be greatly appreciated.
External Display Not Detected After macOS Catalina Update
