APP, make sure all of your calibration frames are 100% compatible with the lights.

[tomato]

To be fair, this issue has been covered quite a lot in the APP forum, but it caught me out recently when I inadvertently used a different profile in NINA with different gain and offset values in the settings. My lights, flats and darkflats were all the same but I had a different offset setting for the darks (essential on a ASI178 camera). APP happily stacked all of the calibration frames and seemingly applied the calibration masters to the lights, except the integrated frame clearly had no flat correction applied. After some head scratching I reran the process omitting the darks and flats were now successfully applied, leaving just the ampglow.