Each time you enter those bank details, they go through a check which can take several days. This could be the issue, once entered, leave those details for eBay to verify.
If you do later need to speak to Customer Services, they're the ones with access to your account and can see if there is some other issue, I recommend using the link below for a Call Back option, and call as close to 8 a.m. on weekdays as possible, as there's more chance then, of Dublin answering.
https://www.ebay.co.uk/help/eua?id=5190
Lines open between 8 a.m. to10 p.m. on weekdays.
9 a.m. to 6 p.m. on weekends
Automated assistants are available outside these hours.
@rosie7987
