If you’ve installed a new bulb and it’s working that means, the other one is blown.
If you installed a new bulb and it isn’t working, check it was working before.
If all above failed, take the working bulb out of the other fog light and put it in the lamp that stopped working.
If no light follow, check connector to see if nothing stuck there or rusted up.
Computer check them both at the same time (at least in my A6) so blown fuse would be out of question.
If nothing above work, wiring might be at fault.
Might be “bumper off” job but following wires of the non working light to the fuse box might be an option. It will eliminate any wire cut or short.
When was the last time you’ve noticed it was working?
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