Hi all, I don't know what I've changed in the K2 config, but now the registered users cannot write comments.
The only ones who can write comments are the two of above whose group is registered.

What should I change in order all the registered users can write comments?

Thanks

SOLUTION:

In K2 parameters, there is a setting that says "Enable K2 User Profile" - you want this to be "Yes" - otherwise, it looks like K2 doesn't assign the user into the default K2 group.

I'm glad you sorted it out.