Jabber as such doesn't have a certificate. It needs tomcat, CallManager and CUP-XMPP certificates to be signed by a CA that the client has in it's trust store. For more information about renewal of UC certificates have a look at this document that I've created about this. https://community.cisco.com/t5/collaboration-voice-and-video/cisco-uc-certificates-renewal-guide/ta-p/4077131
