Why doesn't tab work in emacs?

Question

emacs

The TAB key in emacs doesn't work at all.
And tabulation, of course, too.
C-hk prints - runs the command yas-expand, which is an alias for - for some command in yasnippet.el.
I want to reassign but can't

(global-set-key (kdb "tab") 'indent-for-tab-command)

When I execute, they write to me that symbols function definition is void: kdb.
I tried "", "TAB", "Tab" - the result is the same.
What else can you try?

Answer 1

Here .