Which USB port are you using? If it is the micro USB on the left side of the remote it is prone to the locating pin in the port getting broken. I use a full sized USB in the bottom of the remote to connect the controller and my iPhone 13 Pro Max...
Unless you really need to fly in a geofenced area I’d stick with the firmware you’ve got. Most of the firmware updates for the Mavic Pro were DJI locking things down rather than adding new features. I’ve also got the original DJI Assistant 2 with...
The micro usb plug is easily inserted upside down but that breaks off the tongue in the socket. One of the first things I did was use a silver marker pen to make the correct plug and socket orientation obvious.
I may be wrong, but back then if you had a brand new battery shipped in hibernation mode, you had to initialize it by charging it with the single charging cord, not with the multi battery strip. Don't know why but it worked. May try that.
The original MP batteries go into a hibernation state if not charged for extended periods. If there is any possibility that they’ll work they can be brought out of hibernation if they are left charging for a few hours.
Don’t try this indoors...