I have the same problem with all of my domains hosted by uberspace.de, the certificates are working fine though in all browsers, for google and facebook:
tibormartini.de
tibor.link
wikiwissen.org
The Card Validator responds to all of them with „ERROR: Fetching the page failed because SSL handshake error.“.
Uberspace is using 4096 bit encryption, so the theory is that this causes problems with Twitter Cards since Twitter supports only 1024 bit encryption afaik?
@jbulava, could you take a look?
Thanks,
Tibor