Hello,
Are you able to connect the working Thumby to the Code IDE? Getting things operational with the working Thumby will help in duplicating it on the one appearing to have issues. This should help you determine how to connect and which cable to use. Also, please make sure you are using a chromium browser with the Code Editor.
Does the charging LED turn on when you plug both Thumbys in? There's a yellow LED by the charging port that will turn on when the battery is charging.
Let me know if that helps!
Cheers,
Réna