I just upgraded GPO's Kontakt from 126.96.36.199 to 188.8.131.52, no problem. The new players are authorized and running.
Then I upgraded my GPO Studio from 1.2 to 2.0, but noticed the Studio player pulls up Kontakt players that seem to be 184.108.40.206 versions according to their "About" information -- is that how it's supposed to be?
I noticed that Studio 2.0 installed itself into the folder /Program Files/Garritan/.
GPO is actually somewhere else, under /Program Files/Garritan Personal Orchestra/, a different folder.
Under Garritan Personal Orchestra, there is a VST folder with the file PersonalOrchestraVST.dll in it that seems to be for version 220.127.116.11, according to the file description. Maybe this file is the problem?
I can't find a new PersonalOrchestraVST.dll file that would be for version 18.104.22.168; was there supposed to be one in the upgrade?
But I did get a new PersonalOrchestraDXi.dll file that seems to be for 22.214.171.124. I don't know anything about DXi versus VST.
I used all the default options for the installations.