Will it stitch even if the panel isn't working?
If it will, then it could be a power to the board issue rather than the board itself.
If it won't, then it likely is the board.
The old Pfaffs had batteries you had to change yearly. If the batteries died - the display wouldn't turn on or act weird, but the machine would stitch. Replace the batteries, and the machine did fine. Just straight sewing didn't depend on memory.
The new machines don't use batteries to store memories - but no power or low power can still be an issue.
Have you tried plugging it in elsewhere? House wiring has been known to go flaky. I had a bad outlet.
Calm down, plug the machine into a known "good" outlet, sit there and try to sew. If it stitches, make a note, if it makes a noise when you turn it on make a note. If any physical button works, make a note. Is the power cord fitting snugly into the connection on the machine, make a note. Anything strange, make a note. Power cord in good condition, make a note. Is it in a hot or cold area, make a note.
Then write all your notes with everything you have tried, and see what a dealer says, or Pfaff says if the FB page has any info. This will help prevent the common "user" error if you have it documented. Hopefully, someone will look at the bigger issue instead of running through the common errors again.
No satisfaction - like the other poster said, take mom shopping for a new machine. You've done everything possible.