Ok, I found the issue. It seems in WordPress 4.6 they now helpfully set the defaults of the date picker to match the date format set on the General options admin page. Unfortunately this allows date formats which can not properly be saved.
I applied a hotfix to your site which will force a compatible date format of the date picker. You will need to force refresh your browser in order for the change to take effect. The next update to Connections will include a better fix.
I hope this helps!