Delegating domain in .ru to he.net nameservers

I'm trying to delegate my domain progopedia.ru to use he.net name servers.

I did the changes via the registrar's web site, and whois lists he.het nameserves since about 10 days ago.

Still, he.het shows me this error when I check delegation:

ERROR: Delegation was not found. Please delegate to ns1, ns2, ns3, ns4 and ns5.he.net then retry. We found ns2.hc.ru, ns1.hc.ru during our search.

Am I missing something?

(I suspect the issue might be specific do .ru domains, because I've done the same for several .com domains without any issues).

ns1 and ns2.hc.ru are still the authoritative DNS servers for this domain. The he.net ones are just secondary ones.

https://mxtoolbox.com/SuperTool.aspx?action=dns%3aprogopedia.ru

This config issue has to be fixed on registrar's side.