I just received the MD-103 adapter yesterday. I attached it to my 12.9” iPad Pro (3rd generation). I was able to read a USB 3 thumb drive with no problems.
However, when I plugged in a USB C charging cable to the power pass-through port, the battery icon on the iPad briefly changed to green (like it was charging) and then went back to white (no longer charging).
I tried various sequences like plugging the USB C power to the adapter first then plugging in the adapter to the iPad and it did the same thing. I then removed the adapter and plugged straight into the power cable I was using and the iPad remained charging. I tested it with two different power adapters and USB-C cables with the same result. I let the adapter with pass-through power connected to my iPad and the battery percentage went down over a few minutes, so it’s definitely not charging.
Is this adapter supposed to allow power pass through on an iPad Pro 12.9” or did I get a defective one? I am currently running iOS 13.6 on the iPad Pro if that makes any difference.