That is most bizarre.
Are you trying to sell again on eBay? Looks like you have returned after a little break from selling.
This may relate to registering or confirming your bank account with eBay's Managed Payments.
Only guesswork here as a member like yourself I have no access to your account or eBay messages, but I do know that sudden action buying or selling on a dormant account raises red flags to eBay as it could be a sign of the account being hijacked, they may just need confirmation that the genuine member has returned.
Contact CS again but only at 8 a.m. on a weekday, when there's more chance of Dublin answering, only speak to them see what they say.
@simobartonchappl_0