Hello,
I have been using the platform for a while but wanted to test this feature now. The problem is that this works for any outside site, but not for my own site/blog.
It would be nice to have a visual presentation of another article a bit more then a simple URL.
The error is the same as OP and the web inspector is reporting error 422 (Failed to load resources).
The site is not in private mode and I have it running for more then a year now with the official Casper theme (with just a few modifications).
Any input on the matter would be helpfull.