Hello,
I feel your pain.
I own a DGT Pegasus and I have pretty much given up using it.
I can start a game with it but after few minutes the unit stops detecting moves and I always have to revert to using my phone to finish the game.
I have found that it is not only limited to Chess.com, it also happen when connecting to DGT own app and playing against the engine.
I have met few people locally who had the same issue with the Pegasus and purchased board from other brands to play online.
There may have been updates in the last few months that fixed the issues that I am not aware of, as I stopped using it about 4-5 months ago.
I tried many times in the past to use DGT eboard with Chess.com but always reverted to normal online due to too many technical issues and lost rating.
I struggle to find any way to test it's actually working with Chess.com. Is the only way to test really while in a live game? In my case whether it says board connected or not connected in Chess.com it never seems to detect any moves. When i tested a few years back at least occasionally it worked.
Looking in the Live Chess 2.2.6 app I can see moves being made, but it doesn't seem to get to chess.com.
I don't even try with Bluetooth anymore, only using USB but doesn't seem much better.
Thanks,
Marcus