Can't save widget

I can't save widget. When I click save, I can see wait circle, and nothing happend. When I visit again widgets section, it's empty.

Then I changed view to Accessibility Mode, and still no luck.

Then I've changed id in functions, because that's the place where I create my widgets, and all those widgets I've tried to add before were in inactive widgets, but still can't save any.

Also theme doesn't show anythyng.

What can I do to make it work?