Comment # 7 on bug 1199964 from Fabian Vogt

(In reply to Sorin Fatu from comment #6)
> It seems disabling IPv6 in network manager also "fixes" the issue. Seems
> like it's trying to do the check via IPv6 and never falls back to IPv4. My
> router doesn't have v6 so it will always fail. I suspect that if it fails a
> v6 check it should try v4 too.

Yes, I observed the same in a VM some weeks ago. If a connection doesn't
actually have IPv6, then it still tries to connect via IPv6 anyway until NM is
restarted.