Macbook- No Wi-Fi Interface / Option

Try booting into Safe Mode.

If Safe Mode does not allow the WiFi to work, then see if you can boot into Internet Recovery Mode using Command + Option + R or boot the Apple Diagnostics which should boot to the online version if you Mac had macOS 10.12.6+ installed (and a working WiFi card). If this works, then you have some sort of software issue.

To look for software issues you can run EtreCheck and post the report here using the "Additional Text" icon which looks like a piece of paper. You will need to download the app from the website using another Mac.

You can also try reinstalling macOS over top of itself. If Internet Recovery Mode doesn't work, then you can create a bootable macOS USB installer if you have access to another Mac.

I did provide some links in one of my earlier posts.

Since you don't have access to another Mac, then your options are very limited. You can try booting into Internet Recovery Mode using Command + Option + R or you can try booting to the local Recovery Mode using Command + R. With either option you just select "Reinstall macOS" which will reinstall macOS over top of itself which should leave your user account(s) and data in tact, but you should always have a good backup just to be safe.

Internet Recovery Mode (Command + Option + R):

https://support.apple.com/kb/HT204904

Recovery Mode (Command + R) -- usually boots to the hidden local recovery partition on your drive (this article isn't as good since Apple only shows Big Sur as an example where everything is different):

https://support.apple.com/kb/HT201314

If you can access Internet Recovery Mode by connecting to the WiFi outside the OS, then it would point to a software or configuration or preference file issue. If you can boot to the online macOS installer, then it would indicate the WiFi card and other hardware is likely good.

A clean install of macOS by first erasing the whole physical drive is another option to eliminate software, configuration, or preference file issues.

Most likely since the WiFi hardware is not visible in the System Profiler this would most likely indicate a bad WiFi card or a bad Logic Board (bad WiFi card is most likely of the two).

Launch the Apple System Profiler by Option-clicking on the Apple menu and selecting the first option. On the left pane select the Network item to see if you can see the physical WiFi hardware listed on the right pane somewhere. If you do not see the hardware information, then the WiFi Card or Logic Board may be defective depending on the exact model of your Mac.

Have you rebooted the Mac and tried to add the WiFi option again?

You can try reinstalling macOS over top of itself or you can install macOS to an external drive for testing.

Can you boot into Internet Recovery Mode using Command + Option + R?

Without confirming WiFi outside of your current macOS boot drive we cannot be certain if you have a hardware issue. Most likely you have a hardware issue of some sort (most likely a bad WiFi card) since the WiFi hardware is not visible or working in Safe Mode.

Oops somehow I was thinking the WiFi hardware was not showing up in the System Profiler.

Download the EtreCheck app using another computer and transfer the app to the broken Mac using a USB stick. Post the EtreCheck report here using the "Additional Text" icon which looks like a piece of paper. This report will give us information about the software installed and the exact model of your Mac.

Otherwise you will need to do one or more of the following:

• Reinstall macOS over top of itself
• Restore your system from a backup made before this problem started
• Perform a clean install of macOS by first erasing the whole physical drive before installing macOS

Unless you have customized network settings on the router or on macOS, the macOS default is to configure for DHCP automatically so you should just connect the Ethernet cable and after a few minutes you should get an IP address (usually something like 192.168.x.x or 10.x.x.x, but if you get 169.x.x.x, then you are not communicating properly with the router).

If you have customized macOS network settings, then either create a new admin user account and log into it to test the Ethernet or you can create a new Network Location in your existing user account so it uses the macOS networking defaults.

You most likely have some third party app that is interfering. Run EtreCheck as I suggested previously and post the report here.

If your Mac doesn't have an Ethernet port, then you will need to use the appropriate Thunderbolt to Gigabit Ethernet Adapter or a USB-C to Gigabit Ethernet Adapter depending on whether your Mac had USB-C ports or the older style Thunderbolt ports.