Diagnosis
Grease has hardened in the filter frame or the locking tabs are bent. The filters are not designed to be removed frequently and can seize.
How to Fix It
Press the filter latch release tab firmly inward. While pressing, grasp the front edge of the filter and pull straight down. Do not wiggle side-to-side. If stuck, use a plastic putty knife to gently work between the filter frame and the microwave underside to break the grease seal.
If That Didn't Work
The metal retaining tabs inside the slot may be bent. Unplug the microwave. Remove the vent grille to access the top of the filter slot. You can gently bend the tabs back into position with needle-nose pliers.
Heads Up
Clean metal grease filters in the dishwasher or with hot, soapy water. Do not operate the vent system without the filters installed.