deleting content since no help was received. Don’t want other people to click into this thread and see no answers.
That message comes up if there’s a problem running the checks. Specifically, if something happens when accessing https://yourdomain.tld/settings/ajax/checksetup.
These checks are ran from the client-side.
Check your browser console under the Network tab. Find (or filter by) the entry for checksetup (note: not setupchecks.js which is the precursor). The error you’re seeing comes up if your server doesn’t give back a 200 HTTP code.