OK, understood, thanks. So, is the certificate signed with MD5 by any chance? There seems to be an issue with this and TLS 1.2.
Still, the odd thing is that SSL seems to be working and negotiated just fine, you just don't get any HTTP passing once the channel has been established. Do you never see data from the client after the ServerHelloDone? If not, that suggests the client is at fault.
Seeing any errors in the logs? You could up the SSL logging to debug via System > Logs > Options or tmsh: 'modify sys db log.ssl.level value debug'. Obviously don't do this on a production VS.