Thank you for the prompt reply.
The game is indeed Everquest. The thread you referred me to, is a thread for a problem that was resolved in April 2022. I have played EQ daily using Multiplicity (which has been excellent for this purpose) for several years, my problem appeared today.
I have indeed tried the mouse from the primary plugged directly to the secondary machine and the lack of zooming (ie using the mouse scroll wheel) persists. I have tried other mouse(s) in both primary and secondary and the problem persists.
Many of EQ's servers have a true box ruleset - hence Multiplicity's popularity with EQ players. Multiplicity allows us to smoothly coordinate multiple characters using multiple computers, as required by the truebox ruleset. The zoom on secondary computers is a pretty big deal and currently I am unable to play more than one character at a time. Apart from this zoom issue, as previously indicated there is also very poor connectivity with Multiplicity reporting that the connection is broken because the secondary took too long to respond.
I have checked that all drivers are updated, all operating systems are up to date, all machines are running the same build of Multiplicity. I am not an IT expert in any way. If there is more I should do please point me in the right direction. Thanks