Pay with a like not working at all

I have managed to get "Pay with a like" to display properly using the temp fix recommended here but now it simply doesn't work at all.

On clicking the "recommend" button the dialog box appears to open properly and the "add comment" button is inactive until a comment is typed (see screen cap 1 and 2) .

On clicking the add comment button, nothing happens. It neither shares to Facebook nor reveals the hidden content.

Please treat this as urgent, this project is now a month over deadline.