If you try to invite a colleague who already is registered as a Ramp user, you will get the following error message: "<email address> is already associated with an active Ramp user. To make changes to their role, visit their profile."
Most likely, this team member signed up for an account before they received an invitation. Email addresses can only be associated with one Ramp account. To invite them, their current account has to be deleted. Reach out to support and we'll help get that sorted.