1.00.2.04j is release 1, the earliest version for 50 which is no longer supported by Avaya. The latest version is 50 release 6. You would have to pay. You cannot upgrade from 50r1 direct to 50r6. You would need to upgrade to 50r2/50r3 first, then upgrade to 50r6.
if the problem is on the PC itself, look for julmar phone.exe, you can use this to see if you can control the phone as a means of troubleshooting it.