Hi,
I've got the same problem - tried both 3.26 and 4.0 with exactly the same issue.
No error messages at any point, but no trace of comment capability anywhere on front end.
The right category is chosen in the settings - obviously I've tried changing this, using both include and exclude - no effect.
The plugin is published, and I'm not prepared to give super admin access I'm afraid!
Sounds like a few people have had this problem, so could you please detail how it was fixed with those who didn't have the wrong categories selected?
Thanks.