Try messaging them in roll20 (their user ids will be listed in the games JSON file) You can get to their roll20 account page with a link like this: <a href="https://app.roll20.net/users/5564288" rel="nofollow">https://app.roll20.net/users/5564288</a> That's yours - just replace the number at the end with their ids. From there you can message them. However, you don't need their permission to edit the sheets, it's just a courtesy to ask. If they are inactive, go ahead and make changes while being careful to not change the sheet in a way that would disrupt people currently using it.