I have this exact same issue with a fleet of Samsung NC240's which are Teradici Tera1 clients.
I have done some tracking and found that lets say user #1 logs into Zero #1 and user #2 logs into Zero #2 all is well. Then they get disconnected and when they try to reconnect they get an error saying they can't connect and to contact the administrator.
However I have proven that as others have stated, the view sessions are still running and you can log into those sessions with either another Zero client or a Windows or Mac PC. So there's no issues with the sessions as such. But if user #1 then tries to log back into their session using Zero #1 it's no go for a period of time like 20-30 mins !!
What's odd is that if user#1 and user#2 swap Zero clients they can both login to their sessions just fine using any other device, other than the one they originally got disconnected on...……….. super weird...…...
Any ideas anyone ?