Forgot to mention. But I had just opened a new Godaddy account, selected a managed WordPress host plan, and imported my site from a self-hosted URL.
Things appeared OK, but no theme editor worked. The public landing pages and associated dashboards were all working as expected.
Something strange with their import, I think. I assume you had similar steps?
So I logged into phpmyadmin from Godaddy and I was able to adjust the rewrite_rules property. I don’t know if I should have done this … BUT … I went to my Godaddy admin panel to change the PHP version to a different value to force a site reload. I don’t know if that was necessary. However, I went from a blank screen for my site-editor (and all the failures you mentioned) to a working site-editor page! Success?
The catch is … that value was re-applied after I cleared it.
Still looking to see what the rhyme or reason is.
