Did you sign in on https://app.tabnine.com/signin and can't manage your subscription?
Do you see this message:
Do you have a Tabnine Teams subscription?
Are you sure you are the team's admin? Are you sure you are signed in with a team admin account?
If yes, contact firstname.lastname@example.org
Do you have a Tabnine one-time old license key or Personal Pro subscription?
Your subscription is not linked to any payment method.
That is the cause of the issue. There are no payment managing issues to perform there.
Did you purchase Tabnine using PayPal?