Intermittent error 521(since last week): Host is up, Firewall allows cloudflare IPs

Hello there @harshinik I’ve unpaused it. I followed that forumn but didn’t discover any issues on the webhost. Looking at the server logs, and no cloudflare requests are blocked. When the 521 error comes up, no requests are actually captured on the server.
A kicker, yesterday, it worked fined during the day (EAT), but started breaking in the evening.