Twitter Card (photo) is showing error in the validator tool, but all tags are valid

[cnjsstong]

I’m trying to add twitter card support for our own image server. Currently the meta tags are like:

<meta name="twitter:card" content="photo">
<meta name="twitter:site" content="@FotoDish">
<meta name="twitter:creator" content="@FotoDish">
<meta name="twitter:title" content="FotoDish">
<meta name="twitter:image:src" content="http://img.fotodish.com/upload/534d5a08a15537a840cafe8e">
<meta name="twitter:domain" content="fotodish.com">

as in http://fdi.sh/i/534d5a08a15537a840cafe8e .

However, the validator tool shows error, while all single items are valid.

Twitter Validator Tool result: http://i.stack.imgur.com/dU4PZ.jpg

What is the issue?

Thank you!

[jbulava]

We cannot reach your http://img.fotodish.com/robots.txt file, and therefore the Twitterbot cannot fetch the photo to render the card. Please see this link for more info: https://dev.twitter.com/docs/cards/troubleshooting#twitterbot