@Gardee32 @majoritasdev is correct here. Sandbox uses an entirely different persistence back-end so the items created there are not available in production.
The Sandbox is great place to run integration tests and ensure you can work with the APIs effectively, but for some things (namely stats and Twitter-hosted creative content) it’s not feasible to work with them in that environment.
You can create and preview the cards in production and use the GET /tweet/preview endpoint to see what it a given tweet or tweet with a card included would look like on multiple Twitter client platforms.