How do I turn on my McAfee firewall after updating to Monterey?

Boot into Safe Mode according to How to use safe mode on your Mac and and turn off the firewall from there. You can also delete any of the files from Safe Mode also. The reboot normally.

NOTE: Safe Mode boot can take up to 3 - 5 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

There is a Contact Support and a Support Community for McAfee link near the top of https://www.mcafee.com/support/?articleId=TS103230&page=shell&shell=article-view

If it was my MacBook Air, I would permanently resolve the issue by uninstalling McAfee and never letting it get anywhere near me again.

Your best course of action would be to uninstall all McAfee and any other security software.

FoxFifth wrote:

If it was my MacBook Air, I would permanently resolve the issue by uninstalling McAfee and never letting it get anywhere near me again.

+1