I recently replaced my Server 2008 R2 Storefront 2.5 VM with a new Server 2012 R2 Storefront 2.6 server.
After replacing, I am finding that users can only launch 1 published application at a time.
Eg, if a user is inside their published desktop & they launch a published app, their published desktop closes.
Then if you relaunch the published desktop, it re-connects to the previous session and you can then see the published app open on the desktop waiting to be used.
I'm guessing I have messed up our session limits in some way. Just not sure where to check. I don't think I have changed anything in the AppCentre. Only change should be the new Storefront.