When I try to place new block by clicking "Place block" button or when I click "Configure" on the block I see no pop-up window as I see in tutorial videos, like here: https://www.youtube.com/watch?v=D2KvCGGtBuk 3:10 and 4:25. It seems that this problem is persistent in other administration menus (like views, when I try to choose view format). How do I enable them? Why aren't they shown?
I'm on Drupal 8.1.1, with Nginx web server, Ubuntu 14.04 x32, DigitalOcean. There are no errors in status report except not protected configuration files and trusted host settings, which will be solved when site opens to public.