Site not accessible in proxy mode

Hello CF! my site is not accessible when proxy mode is turned on, but the site itself works fine and is accessible in DNS only mode. The browser returns nothing (not a 522) in proxy mode. And also my VPS provider does not block Cloudflare (in fact the VPS provider also uses cloudflare). Could not find a reason. My site works fine previously and the problem seems to come after I renewed the SSL license. (it is currently within valid period).

If your site is working fine in DNS only mode, then why are u worrying.
What is your domain address?

because CDN is all about the proxy mode, right? In DNS only mode I am not using the CDN.
domain is, it’s very weak in security (literally no security measure in the VPS) so I need CDN to protect it.