Can't click on any element on the scene

Cheers. I have got a terrible problem.
I was making a game and all was fine.
There are UI Texts (add Button Script) on the scene. When a player clicks on a UI text, it changes the sprite. (there is a script what start with OnClick() )
All UI text are in Canvas with order in layer equals 0.
All works.
Suddenly, after one of my actions all elements lost clickability.
I set debuglogs: troubles in the click, not in the script.
I remove my changes and new elements. But problem is stay.
Even if I add a test button, it can’t click.

I don’t know what doing with it. Please, sent me some ideas.

I would create an empty scene and add a Canvas. This adds a canvas with default settings and an eventsystem (which might be missing or disabled in your scene?) with default settings.
compare them and see if unmatching settings cause that problem.