the bank has taken back the refund for no reason.
Banks don't take back payments for no reason. It's usually because a chargeback was issued or because the payment was taken from fraudulent funds.They must have given you someexplanation - if not, ask for one.
With absolutley no information it's hard to advise you. You haven't even told us whether the seller refunded you direct, or through eBay's resolution centre. It's unlikely that a payment made through eBay would be reversed, so my guess is that the seller refunded you direct.
In any case, whoever made this payment now owes you the money again. You need to take it up with them, as you would any unpaid debt. Unless eBay itself was involved in the original refund they will not get involved.
