Help my) ERR_HTTP2_PROTOCOL_ERROR

Ok, I connected literally today and in the first half of the day everything worked, but at some point I found an error " ERR_HTTP2_PROTOCOL_ERROR "
I visited the site changing IP and then I found the error “520”
It must be that I didn’t configure something correctly, the fact is that I can’t find a video explaining what needs to be done after I changed ns records at the registrar. Oh, I also tried to temporarily suspend Cloudflare, waited a few hours, but the situation has not changed.
My site returned to working condition only after I returned ns records of my registrar.
P.S Sorry for my English, please)

What is the domain?

If you :search: for 520 #CommunityTip, you’ll find a tip with some suggestions to fix the 520 error.