502 error after server migration

We moved to our sever at new service provider, since then we facing 520 and 502 error multiple times in day. For example just now we faced one

it comes and gone in few second.

We already added all cloudflare ips in allowlist

May I ask if it’s the PHP application or? :thinking:

May I ask have you tried checking with the steps from below article?

Therefore, have you checked your access or error log at your origin host/server for any clue?

Any feedback from your new service provider?

Is the port used compatible with Cloudflare proxy :orange: ?

Is the SSL certificate valid?

Therefore, have you checked your access or error log at your origin host/server for any clue?
Answer: On our server log, we don’t able to find anything.

Any feedback from your new service provider?
When they pause cloudflare, we don’t get any issue. But with cloudflare on we started getting issue.

Is the port used compatible with Cloudflare proxy :orange: ?
This i don’t know, can you tell how to check

Is the SSL certificate valid?
yes

New update:-
When we stop http/2 on the server, issue is fixed. My server admin said

They saying The provided Apache module is already installed and functioning correctly on the server. There is a possibility of conflict with the Cloudflare HTTP/2 module. You can verify the status using the following website: HTTP/2 Test - Verify HTTP/2 Support | KeyCDN Tools

now what to do?