Sounds like you haven't signed up for  the new system of Managed Payments. There would have been various messages/reminders from Ebay. If I remember correctly, there was also a banner in the Seller Hub. I was moved onto the new system in July last year, but had been getting reminders to sign up for more than 6 months prior.

If that is the case, you won't be able to do anything until you comply with the requirements.

Customer Service are useless - don't rely on them for help.