We are just normal members here, so we cannot solve the issue. We can only give advice.
If the card is past the expiry date, I don't know if even eBay can help.
If not, you will have to contact them, but it seems to be more complicated now. You have to click on help at the top of any eBay page and a window will open with a bot asking you to explain the problem. I don't know how useful this bot is, as it is new, but you will have to try to tell the bot that you want to speak to a human... Good luck with that.
PS: I have never used a gift card, but I don't think it is a good idea to share its number on a public forum.
