user cannot see a category

I am currently at 1 year of experience using SN.
And today I ran into this weird situation.

There is a user that is not able to see a specific "Category" in our Catalog.
This "Category" has no roles and other users can see it.
This user is member of a group, and other members are able to see this "Category", but him.

I have removed groups and added him again into the groups.
I have removed roles and added him the roles back.

I have removed him from the domain and added him back into the domain.

I have created a new user with the same roles and properties as this "bad user" and the new user is able to see the "Category".

Simply I have ran out of ideas on what to do.

This user is not able to see such "Category".

Ideas or opinions are very welcome!