Taxonomy filters don't display results - Drupal 7
So far I've found the right solution to this issue. I will write down it as who will have the same problem can sort it out.

To solve this problem I was just needing to create again the panel-page that I've used to create the taxonomy pages.

Why I was needing to do it? - It's simple, because when there's a new update if you have any entity that is pointing to a module's variable or whatever about that module and something is obviously changed in its implementation after the update, then this entity is pointing to the old representation of that variable/whatever of that module, so obviously drupal will show you an empty set as a result of a normal query.

I hope that this can help someone on the way in the future.

Have a good day drupalers!!
See ya next time ;)