Articles 'cannot be crawled by facebook servers'?

I am still in the process of building my first wordpress site, but so far I’m getting error messages on all of my articles, like this: https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Fwww.jupiter-rising.co.uk%2Farticles%2Ffive-steps-to-a-rollicking-mercury-retrograde%2F%3Fpreview%3Dtrue%26preview_id%3D1209%26preview_nonce%3Dd655d00573

I follow the link, but being a novice I have no idea about SEO or what to do about this issue, although I think it’s important as if people were to share my posts (or rather articles, I don’t have a blog) all that will show up is this error link:
https://www.facebook.com/sharer/sharer.php?u=http%3A%2F%2Fwww.jupiter-rising.co.uk%2Farticles%2Ffive-steps-to-a-rollicking-mercury-retrograde%2F%3Fpreview%3Dtrue%26preview_id%3D1209%26preview_nonce%3Dd655d00573
! Can you help?

Thanks,

Alison
My site (in progress) is: https://www.jupiter-rising.co.uk