Diagnosis
The filter isn't user-accessible in a traditional sense. The MVH uses a permanent, washable filter that's fixed behind the rear intake grill, which isn't designed to be removed by the owner.
How to Fix It
To clean it, you clean the entire unit. 1) Unplug it and let it cool. 2) Use the brush attachment on your vacuum to thoroughly clean the large rear intake grill and the front outlet. 3) For a deeper clean, use a can of compressed air to blow dust *out* through the front grill (do this outside if possible). 4) You can also lightly wipe the grills with a damp cloth, but don't let moisture drip inside.
If That Didn't Work
If performance is still poor after cleaning, the issue might be internal dust on the fan blade or heating elements, which isn't meant to be cleaned by users. That's a sign to contact support.
Heads Up
Don't try to pry off the rear grill to get to the filter. It's not meant to come off and you'll break the plastic clips, voiding your warranty. The design is for surface cleaning only.