Connection added
Can't add connection
Console warnings:
Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at https://eatkibbeling6.wordpress.com/wp-admin/options-general.php?page=sharing&action=error&service=facebook&id=20594016. (Reason: CORS header 'Access-Control-Allow-Origin' missing).
Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at https://eatkibbeling6.wordpress.com/wp-admin/options-general.php?page=sharing&action=error&service=facebook&id=20594016. (Reason: CORS request did not succeed).
Chrome and Firefox on macOS

Just to note, I am able to reproduce it as well.

I had this too, and a user did as well.
support reference: 4589696-hc
Another user report here: 1314279-zen
Ticket opened here for follow up on this issue: 1319744-zen after having been reported at 560433-hc
This bug is actually caused on the server side, I am in the process of fixing. Going to go ahead a close this in favor of the fix at D16801-code.
Most helpful comment
This bug is actually caused on the server side, I am in the process of fixing. Going to go ahead a close this in favor of the fix at D16801-code.