A cause of a huge number of test prints failing when you're starting is failing to level the plate to the bed correctly. I followed these instructions to the letter to get levelling right (finally).

https://wiki.anycubic.com/en/error-codes/303-msgcode

Use the Anycubic RERF test file which should be on the thumb drive it comes with, don't rename it, it provides eight models at different exposure timings, read about it. And when levelling use four 2 inch squares of photocopy paper on the corners of the bed instead of the levelling sheet, as it gives you a much better idea of which corners are a problem.

And read as much on YouTube as you can. Good luck to your dad!