Cable connection not working anymore on EDGE 820.

My Edge 820 is increasingly problematic. Battery depletion, navigation works less and less (bugs, freeze during the ride, 20 minutes to load a stored ride, etc). The device i of course not new, but I used it very carefully and in general it was not used too much. One other problem (maybe related?) is that I cannot connect using the cable. I can upload rides via my phone, but if I connect to the computer via the cable, the device does not appear. 

I did not care too much about this until recently, because I hope that if I could update the firmware some of the bugs would disappear. This is not my main device anymore (I just bought a 1040), but I still plan tu use it, especially for city commuting, and I would like it to work better

One thing I did not do is the factory reset. How is it done on these devices? And any other suggestions?

Thanks!