The customer is trying to add a new admin to their account but when he enters the teammate's email address it says he is already part of another organization. I double checked and yes, the email that he is trying to register is already associated to another account. He's their marketing agency owner. He's not an employee with their company. I advised the customer to provide him another email address associated with the company but he said that they can't.
Let’s say that the email address in question is example@email.com, a workaround could be using an email alias such as example+drift@email.com and it would allow for him to be registered under their account as if it were a different address.
https://drift.lightning.force.com/lightning/r/Case/500PL000009lU41YAE/view
https://drift.slack.com/archives/C80EAM7R8/p1714676852438189