How to fix "Remember logins for sites" checkbox in options is greyed out in FireFox

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 or otherwise make changes.

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

You can also inspect the signon.rememberSignons pref on the about:config page to see if you can toggle the value to true.

You can also fix it by

How to create a new Firefox profile