The fact that your Auxiliary Input Jack is under the dash suggests that there may be an aftermarket solution involved, as the factory jack would be located in the center console storage box. What is the brand and model of your Auxiliary Input adapter?
First step is to visually inspect all the wires behind the sound system, assuming of course you've confirmed it's not your device or the plug itself that's the problem.
And here we sit waiting for clarification... Wondering if we got ghosted again? Hate it when that happens...
Sorry...I meant the '12v adapter' under the dash is not working. FIXED = It was fuse #21, located in the inside car fuse box.
I always have something plugged into that 12v adapter, phone charger,radar detector,etc. ***That mini low profile fuse was hard to find and kind of a pain to install...