it could be the cable you are using. i have a universal cable that has a left and right toggle switch on the OBD2 connector. i had to have my laptop at the ISTA screen, USB plugged in, and then plug into the OBD2 for it to read. yes I too had issues trying to get it to connect, its in the configuration.
if you buy a K+D can cable, say for example from
https://www.bimmergeeks.net/product-...dition-k-dcan1
they usually give you instructions on how to configure your laptops COM port so that it goes to COM1 and everything matches up for ISTA to work.