Hello,
sorry for my english.
I have a problem with the component K2, I installed it and set it all for it to work properly.
So far no problem, but when I try to assign a different template for a specific category, so I click to view the details of an item template that shows me is the default.

Below I have outlined what happens

Home template1 OK
Category A template2 OK
Detail Item Category A instead of displaying it with the template2 visaulizzo with template1 Error

I would be really grateful to everyone if you could somehow give me some tips
Thank you and we hope to soon

nobody can help me please!!! :(

When you say template do you mean K2 template or Joomla! template?
A link to your site would be also helpful in order to understand your problem better..

Thank you.

Thank you for having responded to me

This is the link to the site if I click on an article opens with another template joomla

www.rstar.it/index.php/index-php-option-com-k2-view-itemlist-layout-category-task-category-id-12/news-events3

Try to exclude this category from the Default template. Just choose to which menu items the Default will show.