I cleaned cache and wpforo cache , i recalculated statistics , i dont know what else to do

Then there is no such issue. It's a device specific issue. Something is wrong with user device or browser. If the notification works fine for you, then it should work fine for all. wpForo works with the same functions for all users. We cannot do a troubleshooting for specific user. It would be better if you ask for some video, which will also show the JS error in the browser. They should press Ctrl+U and open the tab before starting the video.

Also, check your plugins and make sure there is no user specific plugin which may cause JS error for certain users or user roles.

I think the notification bell is used in no-forum pages, and they are cached by WP Optimize page cache plugin. It works fine on forum pages because you've excluded the forum page from WP Optimize page cache plugin.

So, if you have a cache plugin you should not display the notification bell on non-forum pages. I think you use the notification widget in other pages.