See:

• https://support.mozilla.org/en-US/kb/password-manager-remember-delete-change-and-import

It shows saved passwords, but does not suggest new!

Is this about the feature to generate a password or about Firefox offering to store a new password ?

• https://support.mozilla.org/en-US/kb/how-generate-secure-password-firefox

Make sure you do not run Firefox in Private Browsing mode.

• https://support.mozilla.org/en-US/kb/private-browsing-use-firefox-without-history
• https://support.mozilla.org/en-US/kb/common-myths-about-private-browsing

This ia about generating new password! There is no option for it when i click on password box of registration page. And I'm not on private window!

You can check the signon.generation prefs on the about:config page.

You can open the about:config page via the location/address bar. You can click the button to "Accept the Risk and Continue".

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

I dosent have a signon.generation at all

Ah. I see you use Firefox 68 ESR. The basic code to generate a secure password landed in Firefox 68, but I think that the user interface supported this in Firefox 70, so with 68 you are out of luck.

• https://searchfox.org/mozilla-esr68/search?q=PasswordGenerator&path=