I know it's "solved" but i wanted to give an explanation in the event someone else sees this. The error indicates that the Client did not accept the server certificate for some reason. it could be that the certificate expired, or that it failed verification. If this is not a public cert, and a self-signed or signed by an internal CA, and since it only affects some clients my money is on that the clients are trying to verify the cert and it is failing verification and therefore rejecting the certificate before any authentication can occur. I can only think of 3 ways to handle this: 1. disable certificate verification on the end system. this is not really recommended as you are opening that system up to MITM attacks, but can be done. this is really an issue if that end system connects to other outside networks. 2. put a certificate signed by a trusted CA on the authenticating server. 3. add the CA that signed the certificate as a trusted CA in the end system.
