2008 audi s6 mmi not working at all

I’ve checked fuses, tried the fibeber optic bypass most loop cabe to the DVD navigation unit. The unit female connecter lights up and blinks but I still have no luck. What else could be making it not turn on??? Amp?radio? Man I’m so freaking mad because I cant even use the backup cam.

My baterry can lose and broke the stud where there
Baterry monitor monitoring unit bolts to. So I welded the stud back m.

Is this an ecu issues onto where I need to reset the ecu. I already pulled the cables off for hours. No luck. Stumped.

Did you replace any fuses or just checked them? Have you checked the codes it’s throwing? My whole system went out a couple of weeks ago after doing some battery work. I had codes for many different issues related to the communication systems. My issue was resolved by checking the fuses. Have you looked at them in all 3 locations?

I am no battery expert, so someone else can chime in, but with the repairs done I wouldn’t be totally confident that the issue is not related to the battery and battery management system.

Which fuse or fuses did you replace and in which fuse box?

I didn’t end up needing to replace any. But I pulled most of them to just check. I checked all 3 fuse boxes. The two up front just pull the covers off where the door normally covers. And there is one in the trunk. They have little fuse diagrams inside and a fuse puller to make it easy.