I'm having difficulties adding a specialized user in flowdock. I filled out the form, but it turns out the email address we had created had not been enabled to receive emails from external addresses. Once we enabled that, and I tried to add the specialized user again, it returned an error message saying the email address "has already been taken". I went into our user list and cancelled the original un-accepted invitation, and then tried to re-add the user again but received the same error message. There are no users set up with this email address. Is there a way to clear out whatever information is making the system think this email address is already in use?