WP Super Cache fails to cache

I’ve had WP Super Cache installed for a couple of months on this site oromoctovethospital.com, along with the WP plugin Autoptimize. For some reason it has stopped caching. I deactivated and deleted WP Super Cache, edited the wpconfig file as suggested in the WP Super Cache installation FAQ, and then reinstalled with PHP caching enabled. When cache is tested, timestamps don’t match, debugging logs show that no pages have been cached, and a list of cache contents shows 0 files. Any ideas what might be wrong? It was caching previously.

https://www.ads-software.com/plugins/wp-super-cache/