Hi Bryan. I ran into this with my Shark after a few years with two cats. At first I smacked the filter on the trash can and tried a soft brush and but the suction barely improved and I worried I was just grinding dust in.
What finally worked was a simple rinse routine. Unplug the vacuum, pop out the foam and felt filters, take them outside and tap off the loose dust, then rinse under lukewarm water until it runs clear. Squeeze gently without twisting and let them air dry completely, usually overnight. Never put a damp filter back in. While they dry, I pull hair off the intake screen and give the HEPA a light tap if the model has one. The next day the suction came right back.
To keep it easy I bought a spare set so I am never waiting on dry time. I used 4+2 Pack which fits the NV350 series and includes foam and felt filters. The only minor drawback is the overnight dry, but with a spare on hand it stays simple and safe.
