Hi,
Ok I just received all the informations. Unfortunately today I am not working on the computer where I have the Private key stored.
So I will not be able to look deeply into this issue until Monday.
But for the moment, I went to your backend and saw that you have an override on the view "category / listing". I was not able to edit it in order to put our default code to see if this is the reason of this issue. So please try to do a backup of that view, remove the override and test.
I really think this can be the reason of that issue.