2020 A4 USB port issue

[ggdt]

I've recently bought a 2020 A4 Avant and am having problems charging my phone via the USB port.

Initially when I plugged my phone into the USB port in front of the gear lever Android Auto would connect my phone to the MMI and the phone would start charging. Recently however although Android Auto is still working fine the phone no longer charges via the USB connection.

I've tried several different phone cables and they all charge the phone for a short time then stop. Today I tried another new cable, again the phone started charging and Android Auto connected initially but after switching the engine off for a few minutes when I returned to the car and re-started it the phone would no longer charge. The phone also charges fine via the 12V socket in the car using the same cable that won't charge it via the USB!

I use google maps as my SatNav but the phone has to be connected via USB for that to appear on the MMI screen. Obviously google drains the phone battery though and as the phone won't charge via USB I then have a low battery by the time I reach my destination!

I'm at a loss as to what's wrong here? Why would USB charging not work when the car can clearly see the phone as it's connecting to Android Auto. Is there some setting in the MMI that prevents you charging a phone via USB?

Does anyone have any ideas as to what could be going wrong? The user manual suggests you should be able to connect a phone to the MMI and charge it at the same time from the USB socket.

Thanks in advance.