Comment form on posts disappears after activation of UM

Hi,

I’ve got a little problem with new UM. Not sure when it came out, but it was working fine before.
The problem is that when I activate the plugin, the comment form disappears on single posts.
When I add a comment to the post via back-end (post editor), the form and comment show up.
So users are unable to comment, if the post wasn’t commented yet.
Only admin can post a comment, then users can.
Is there some setting for that?
Or is it some bug or incompatibility with my theme?

Best regards.