I had some issues with Oaisys a while ago but it was more like bugs in the software as We upgraded and could not download the client piece . What you describe is sounding more like something is blocking it from starting . Is Oaisys in the same subnet as the PC you are trying to connect with ? We upgraded because due to recording issues but not with connection issues except after we upgraded we found an issue with the client as Oaisys claims its a known issue with downloading the client portion , We had some issues trying to connect to the upgraded version and had to use a hidden URL . I am checking my notes to see if I can find it but the Web URL was wrong in the new software .
What version are you running ?
Whats your network look like ?
Subnets , Routers etc .
Your GPO , Is it an internal firewall or does it scan your whole network , and was it installed on the same day you noticed the issues ??
Previous experience , especially with Sonic wall , Even though your GPO unit may have been disconnected , I would remove it OFF the network and test , If this unit was installed close to the same time you started experiencing issues .
Hope this helps !