Concur w/OT11 above, a single brake light going out on one side is unlikely to be a fuse problem. Unless your owners manual says differently, dismiss the fuse idea. My guess is the socket is a little corroded and not making good electrical contact with the new bulb. I replaced a license plate bulb on my aged truck a couple months ago, and had great difficulty to get the new bulb to work b/c of that same problem. You may need to look at the socket w/a magnifying glass to see where the corrosion is occurring. I checked for a ground problem too, but probing with an ohm meter showed the ground was making good contact with the frame already. Probing w/a volt meter showed I was getting proper voltage, but the bulb wouldn’t light, b/c of poor electrical contact b/t the bulb and socket. This didn’t work in my case, but sometimse you can clean up a corroded socket by rubbing it with a pencil eraser.