Holly cow I can not believe I have to post this for help on changing "light bulb"!

A6 2001 2.8 Avant Quattro Wagon : Started as RT Rear brake light out. I keep getting recommended conflicting bulbs for replacement.

Tried 3 different bulb # and none solved problem. Directional as part of same bulb works.

Then lost the left side bulb. When I pulled that bulb that has been working some how for past three yrs I looked and it was a simple 1156 bulb?

So I tried replacing both with 1156 bulbs with no luck!

I check a fuse: 10 amp fuse # 13 that said for brake lights! Fuse ok!

Anyone else ever have this simple problem that has become a real nightmare????

Could a bad switch be problem but why originally only lost back rt side?

Is there another Fuse I missed?

Please anyone with idea? Hate like hell to go to dealer for a light bulb?