You attempt to start an SSL channel with mutual authentification (receiver has SSLCAUTH(REQUIRED)) and you get this error message.
This may happen when the SSL certificates do not have the correct Key Usage attributes.
If you change SSLCAUTH to OPTIONAL the channel starts!
Then the Key Usage must be:
- Either blank, OR
- If not blank, it must include HANDSHAKE
For instance, a certificate with this Key Usage will not work: Key Usage: DATAENCRYPT
This will work: Key Usage: HANDSHAKE, DATAENCRYPT
More info here.