Could try a Two-Button reset. Press the two "green dot" buttons - Mode and CSM - and hold for at least 2 seconds. Will reset many settings back to default, just in case you changed something and forgot. Not sure what it would be, but worth a shot.

I'm sure some others with more knowledge will chime in here soon.

Regarding using a brush. It should be relatively clean, the brush is used to dislodge something that may have slightly adhered to the surface, once it is moving, the blower can whisk it away. Best to hold the camera with the lens opening pointing down while you do this cleaning, then, hopefully any debris will fall out.