For me, the quick fix was to make sure I have the correct “Settings” WordPress Address URL and Site Address URL, make sure it’s correct, especially http vs https …
So what happened was I tried to use WP Faster Cache plugin, I followed the direction and activated the Cache (enabled) but after a few days I noticed there isn’t any cache files folders created in the “cache” directly. I checked my other blog (wordpress) and those are working fine.
I compare the Settings configuration in term of path directories then noticed the differences, http vs https. I am using Cloudflare at the moment for the https. However my blog Settings Address URL wasn’t https, so I updated it and now it is working correctly.