Update.

I think that problem might be related to built-in password manager. Reason? Unable to change master password (previously not set). However troubleshooting and renaming files not helps (firefox is not creating new).

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance
• Do NOT click the Reset button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

You can open the Browser Console (Firefox/Tools > Web Developer). Paste the JavaScript code in the command line and press the Enter key to evaluate the code.

• You can toggle devtools.chrome.enabled to true on the about:config page to enable the command line
• https://developer.mozilla.org/Tools/Browser_Console#Browser_Console_command_line

Paste the lines one at a time to see the response.

Services.logins.getAllLogins().length
Services.logins.countLogins("", "", "")

Thanks for reply.

So, safe mode on, hardware support in preferences off, problem still occurs (add-ons and themes disabled). When sync is enabled for everything except tabs and passwords there is no errors. When it's enabled just for passwords, error appears (no surprise here).

Both commands gives the same result (regardless of safe mode status): ReferenceError: Services is not defined

There is a tip, but that might be a side effect - when FF stars with Sync on at the begging there is login/password error and I need to sign in (so he can't store even sync password) - except situation when sync account is disconnected.

Bump.

Are you using a Firefox version from the Mozilla server or a version from the Linux repositories that is possibly modified?

Try the version from the official Mozilla server if you currently use a version from the repositories of your Linux distribution.

Does the Firefox Password Manager work properly?

Did you make sure that your are logged on to the software security device by entering the master password when prompted?