From what I understand, this isn’t even a server problem. The error code and message seem to indicate a problem with the REST API setup in WordPress, and I can see this on multiple sites.
As for caching, I get different results from different API queries, whether or not anything is excluded, so that’s not it either.
To exclude any hosting account specific issues, I’ve just tested on another site and gotten the same result. To be sure, this site has NO caching or page optimisation in effect.
On a previously configured site with fonts being listed, simply clicking Save & Optimize returns a “No (additional) fonts” message. Then, after emptying the cache directory, the messages changes to “No route”.
Perhaps the first message is OK and something happens when the cache directory is cleared?
Could this be about the timing of REST API calls relative to when routes are registered (I’m really fishing here)?
Again, a debugging snippet should go a long way towards resolving this, so I’d really appreciate help coming up with one. Calling OMGF functions in this snippet is OK, so this can be based on plugin code with some debugging enhancements.
Alternatively, I’m happy to hack the plugin on my test sites and insert code, if it will help figure out what’s going on.