This is what I can quickly find for troubleshooting:
CPAP Troubleshooting Guide
My next question would be: Does yours assist breathing in, or in and out?
I've never seen a mask nor CPAP machine but have worn a respirator, the technique to determine the properfit may apply.
At least with a respirator, you block the intake and try to breathe in. If there is resistance then that way is OK.
You can also block the exhale port and try to breathe out. There should be resistance.
You want the mask comfortable, but not tight.
Respiratory fit testing is done with an oil that smells. Facial hair, for instance, is a no no. Is that a factor in your case?