Why can I not access retail customers' Cookiebot account?

If you have invited a customer, and they accepted your invitation, clicking ‘Manage’ will give you access to the customer’s account and configuration.
However, if you are instead redirected to a page prompting you to add payment details – which cannot be bypassed – then this is likely due to the customer not having provided payment information yet.

If the customer has added a domain to the account with more than 50 pages, a Premium subscription is required after the 14-day trial period expires. At this time the customer must add payment information to continue using Cookiebot CMP under a Premium (paid) subscription.

Anyone trying to access the account (this includes both you and the customer), will be redirected to the payment information page.
If this is the case, please inform the customer to add payment information so you (and the customer) can regain access to the account.