Astrobert Plate solving works in preview but no longer in Polar Alignment.
Check the different exposure value (exposure time and gain).
Hint: before you start guiding, it is best not to increase the exposure time beyond two or three seconds. Instead, increase the gain of the camera (especially now that you can add an extra 20 dB of gain for the ASI2600).
The reason is that any elongation of the stars will cause star detection to fail, and thus cause plate solve to fail. I see a lot of the Facebook crowd complain about not being able to plate solve, and instead of increasing the gain, the usual "advice" is to increase the exposure time (snicker).
Once guiding is started, however, star shapes should allow you to use longer exposures, but be sure to turn guiding off before you apply "sync and goto" after a plate solve -- the mount would either not move, or locks up and requiring a mount reboot :-). Not a problem with polar alignment, since you are not moving the RA and declination motors.
Remember to change the gain back after polar alignment and plate solves :-).