Use a laptop / PC not the app or mobile browser, and Chrome, perhaps clear cache and cookies too. Then try and add new bank details with the link below. Be aware, it may take a few days for eBay to verify those details before they become operational for receiving payouts.
https://ppcapp.ebay.co.uk/myppc/wallet/list
If there is still an issue contact eBay Customer Services, if you do this now there's more chance of Dublin answering.
This is the easiest and quickest way to contact eBay Customer Services from the link below, for a Call Back option. I do recommend contacting CS very first thing in the morning when the lines first open, as there's more chance of Dublin answering
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
Lines open between 8 a.m. to 10 p.m. on weekdays.
9 a.m. to 6 p.m. on weekends.
@chimaera1968