GBIT not possible in the app due to the message "This transaction has been fully refunded(...)"

Anyone who knows what this means: “This transaction has been fully refunded and cannot Go Back In Time”? I try to GBIT with a transaction less than 5000£ but it is not possible. The amount has not been refunded on my account/card.

How long time is the transaction ? And did you received a mail ?
Because if it’s refunded fully or even partially then you cannot do GBIT