Hi Carl, you are using meta tags that require values when added to a page. If you are not using the app tags, domain tag, or creator tag, then delete these entirely and your card should validate.
To request approval, go to the cards validator (https://dev.twitter.com/docs/cards/validation/validator) and you’ll notice a tab that says “Validate & Apply”. Enter any URL on your domain that uses a Twitter card. If it validates and is approved, then any URL on your domain will be able to use that card type.
Simply tweet with a URL to use a card. A card is automatically attached to any tweet that includes a URL with working meta tags in its source.