Transferring a project to another user is a two-step process: first, add them as a project member, and once they accept that invite, click the three dots next to their name in the project's Members settings and select "Transfer Ownership" - this sends a separate confirmation email they must accept within 24 hours. If your client accepted the membership invite but you haven't yet initiated the transfer via that menu, that would explain the pending state. Also note that both accounts must have an active Hobby or Pro subscription for the transfer to go through. Full details are in our transfer docs.