“Mask needs adjustment”

I’ve been using a cpap for 4 months. I consistently get “mask needs adjustment” message. I’ve changed masks and pillows repeatedly. My AHI’s are low. Is the cpap providing any benefit despite the maladjusted masks?

It means that it is leaking badly and if leaking badly it is entirely possible that your nice low AHI number is meaningless if the leak is so bad that the machine can't sense events properly and correctly.
So it depends on just how bad the leak is as to how much it matters.

Consistent leaks can make the therapy less comfortable or disturb your sleep, even if the numbers look good. You might still wake up more or feel less rested. If that’s the case, trying different mask types (like nasal vs. full-face), adjusting the headgear tension, or using a CPAP mask liner could help minimize those leaks