When they tried to use the card I bought it says the code cannot be found

[eburtonlab]

eBay gift cards can take up to four hours to be activated from the time of purchase.

If it has been longer than that and the card is still not working, take the card and receipt back to the retailer where you purchased it and have them check that the card was properly activated.

https://pages.ebay.com/giftcard/faqs.html