Incompatible versions of Avaya Computer Telephony client and server
Active Telephony components will fail if you use Avaya Computer Telephony client software Version 9.5 with Avaya Computer Telephony server software Version 9.1 . If this occurs, upgrade your server software to 9.5 or change your client software to 9.1.
At all times it is preferable to have the version numbers of both the Avaya CT Server and Client components matched.