Your 12vdc battery may be toast. Normally, it is recharged by the main batteries via a DC-DC converter. But, if it is way gone, when you plug it into an EVSE, there is an emergency 12vdc trickle charger. That may or may not charge the 12vdc battery enough to make things return to normal. THat whole procedure can take many hours, but overnight, if it is the battery, it would have likely worked.
So, you could pull the HV disconnect, remove the 12vdc battery and take it somewhere to be checked, or, if you have a fancier battery charger, put that on the now disconnected battery and see if it can revive your battery. If it's bad, replace it. If it's good, you'll probably have to have it towed to a dealer for them to diagnose your problem.
All of the computers essentially run off of 12vdc, so if that battery is bad, you won't be able to start things up.
2011 535i x-drive GT, 2014 i3 BEV
Soon (hopefully!) A 2021 X5 45e will replace the above