If you started with Try it on the home page and then finished your account, Magpie still treated it as unfinished. A team admin who tried to add you saw "That person needs a Magpie account before you can add them", and you could not be added as an accountant. Finished accounts are now ordinary accounts, including ones finished before this change.
Accounts started with Try it can join teams
An account started with Try it and finished with an email address, Google, LinkedIn or Apple can now be added to a team or as an accountant.