I am trying to give access to my group to someone that already has a dropbox account with another group. I get the error that the person can't be added because he is a member of another group. How can I add him to my group?
If I understood correctly and you're indeed a Team Admin on a Dropbox for Business team account and you're trying to add someone to your team (i.e. group as you mentioned) with an email address they're already using for another team account, you'll need to invite them to your team on another email address since there is no way to be a part of two different team accounts with the same email address (and therefore the same Dropbox account).
If they'd like to convert their account back to an individual one, they'll need to ask their Admin to do it from their end. From that point you'll be able to add this person to your team with the email address that's already in use if needed indeed.
I hope this makes sense to you while I'm always at your disposal for any further questions you might have.
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