How to fix "Failed to attach link" in OK.ru?

Question

Social media

For all pages of the site we get this error. Until recently, links to the site were attached normally.
How to treat it?

Answer 1

When trying to load pages from this domain, we get an SSL certificate validation error.
The checkers say that the certificate chain is invalid: A valid Root CA Certificate could not be located, the certificate will likely display browser warnings.