SSL HandShake exception

Question

I use SSL connection to connect web client to server. It works without any problem for a long time. But from yesterday it gives following error can anyone tell me the reason

Answer 1

This 'certificate_unknown' is a very misleading error message. This is the same error message thrown when a certificate has expired even if it is in the truststore. I suggest checking the expiration date of the certificate before you waste your time on anything else.