Hi there!
If you’re trying to use the card to purchase coins on the website, you’ll probably have to get some information from Vanilla or Visa to do so (there should be a website somewhere on the card or some instructions that came with the card). There’s often an activation or registration process on these cards that you’ll have to complete on their website before you can use the card online.
You can also contact the card issuer to see if you need to use a specific zip code or address for the card, rather than your own (which is probably not linked to the gift card at all).
If you’re trying to make these purchases through our app and are still having trouble after ensuring these things, you’ll have to contact Google Play, as it’s an issue with adding the gift card as a payment method and can’t be fixed on Tapas’ end.
Worst case scenario, if all else is failing, we can also recommend that you use the Visa/Vanilla card to get a Google Play card at the store, and load the credit into your account that way. This may give you fewer hoops to jump through.