Cards validation and request approval


I’m a newbie for using twitter cards.

I have a page with metadata to use twitter cards.
The metadata looks like this:

The Twitter Card Validator says, it’s ok. But when I do a Request Approval, the answer from twitter is:

"The URL you provided for to use the summary card did not validate. Please make sure the page contains valid metadata, then reapply for a Twitter card. "

I have used other combinations too - without postive effects.
I have no idea, whats wrong.

Can anyone give a tip?

Many greetings,