Are you still seeing a problem? If you’ve just changed the nameservers at your registrar it may take up to 24 hours for changes in authoritative nameservers to be picked up.
I solved the problem with the registrar
It was a DNSSEC issue
even though I never set it up and there was no problem until the registrar change, there was indeed a bogus DS entry for this domain
I properly enabled DNSSEC on cloudflare and on the registrar and now everything is ok
Thanks for checking anyway