I've noticed some recent changes to using a DGT board on chess.com. In the past you had to be a beta member. I no longer think this is a requirement. I checked if I was a beta member, it asked if I wanted to "join" meaning, I was not a member and the board still works. Additionally, you had to play your games in "Live Chess" versus "Play". Now, it will work in either option, but currently the chess.com voice commentary (Google Chrome extension that announces the moves) works only in "Play" and is no longer working in "Live Chess".
Long story short: Use the "Play" menu option to get all the functionality you need to use a DGT board. Just make sure when in "Play" you select "DGT Board" under Settings -> Board
https://support.chess.com/article/1257-how-can-i-play-with-a-dgt-board
I've noticed some recent changes to using a DGT board on chess.com. In the past you had to be a beta member. I no longer think this is a requirement. I checked if I was a beta member, it asked if I wanted to "join" meaning, I was not a member and the board still works. Additionally, you had to play your games in "Live Chess" versus "Play". Now, it will work in either option, but currently the chess.com voice commentary (Google Chrome extension that announces the moves) works only in "Play" and is no longer working in "Live Chess".
Long story short: Use the "Play" menu option to get all the functionality you need to use a DGT board. Just make sure when in "Play" you select "DGT Board" under Settings -> Board