Tandem 6530 is not currently supported due to its distinct set of escape sequences, but we can add support for it with your help just as we added Pick and Wyse 60 support in the past.
If you can provide us with a temporary test account on a Tandem OS, it would be the easiest way. Otherwise please use our WinFormClient sample, enable recording (Tools->Start recording), connect to a Tandem and do some work. When you exit the session, please send us the recorded session for analysis.
If you have any Tandem escape sequence specification, it would be very useful for us as well.
Also, you can try to connect with the WinFormClient sample to your Tandem in ANSI Mode (one of Tandem’s three CONV/BLOCK/ANSI). Maybe it will work without any problems.