Struggling with groundcontrol shutting down and calibration

Hi People

Arduino
Maslow firmware 1.26
Ground control 1,26

I’ve tried loads to resolve my issue but I’m no PC expert, when i start up ground control it loads and connects but as soon as it is ready i get a pop up and then the program closes. Pop up is unable to find vailed machine position for chain lengths 3020 15. 0 00 please set chain length. i think this is a red herring.
If while connecting to the Arduino i press Stop it times the connection out and i can move the motors etc, once i do calibration and set chain length the program also shuts down.

any advise would be appreciated.
Dave