I'm working to upgrade a site from 9.5.11 to 10.1.6. I followed the instructions provided here:
The upgrade went fine using composer, but when I visit the site after the upgrade I noticed that the site's theme isn't being loaded. The site is displayed as a long series of menus with content at the bottom of my browser window. I flushed all caches, still no luck. On a whim, I put the site back into maintenance mode, and suddenly everything looks fine again. The problem reappears if I bring the site out of maintenance mode.
I have full access to all menus while viewing the theme-less site, and I've tried switching themes, including trying to use the default Olivero theme, to see if that made a difference. It doesn't. Did I miss something with the upgrade? Can anyone help identify the problem?