I was getting the error “Herd could not find a valid PHP file to serve the … project” on a Craft CMS project that was working. It was working fine then suddenly stopped.

Restarted Herd, restarted laptop, nothing worked. Still the same.

Other sites worked, just this paricular one wouldn’t.

Deleted the cpresources contents from web and refreshed. I assume something had been cached and possibly broke during the caching process?