TAC Xenta OP just shows "Connecting to Xenta base unit"
I have a TAC Xenta OP and a TAC Xenta 301 (controlling the heating system).
When connecting the two (with the DP-Jack), the OP just shows "Connecting to Xenta base unit". Additionally I recognize, that the font is quite faded.
A technician with another OP could connect to the Xenta 301 just fine, but I remember his OP having a blue instead of the red frame. So I don't know if it also was an TAC Xenta OP.
Are there incompatible Versions of TAC Xenta OP and TAC Xenta 301?
How could I check the OP?
I would appreciate any hint.
P.S.: As I just want to check the parameters of the heating system from time to time: is there another way, like through the RS232 interface (I guess that is only for programming the Xenta) or with an software-emulated OP?