You’re most welcome! That’s great to hear the above method worked fine for you Sarah! 
So most likely previously any of your plugin(s) might not fully compatible to run on PHP 8.0 (and had to switch to PHP 7.4 first, and you could then work on it/re-registered/updated plugin(s), and was then able to switch back to PHP 8.0).
About the insecure warning, since you mentioned Mac OSX Monterey , I remember about similar issue with the SSL cert on Mac OS (on Ventura though) - and am wondering if this solution here may also work to solve the case you’re experiencing perhaps.
Cheers,
Agus