Thanks for the input, kjodle. However, flushing didn’t change anything. The Inspector does say that “CSS Grid is not in use on this page, though.
How can I re-apply any missing style.css files?
Could I simply backup my content, re-install WP and restore content?
Meanwhile I found this video on YouTube which describes this very situation.
According to this, the solution is simply:
1. In WP admin go to Settings and update the two directory settings to the root directory
2. Copy all files from the WP sub directory to the root
3. Rename (or delete) the WP sub directory
I am trying this out right now… 🙂
