The PicoScope 3203D MSO is not an Automotive Scope, does not have the necessary protection to use it in this environment, and as such will not work with the Automotive Software. If you really need access to the Waveform Library contact the supplier of the scope and see if it is possible to exchange ...
As you have used A-B you need to use the Invert option in the decoder setup, alternatively create the maths channel as CanHigh - CanLow which would be B-A
You will need to change the Baud Rate to 250kbaud as shown here