Open Firefox. Do you have the Firefox icon on your quick launch? Right-click on it, and select Open New Window. Now close the First window. Wait a few moments, then restart the browser.

Thank you for your solution puts this does not work.

https://support.mozilla.org/en-US/kb/changes-toolbars-and-window-sizes-are-not-saved You may have corrupt xulstore.json file.

Close Firefox. Open your file browser to this hidden location:

• Mac: *~/Library/Application Support/Firefox/Profiles
• Linux: *~/.mozilla/firefox/Profiles
• Windows: %AppData%\Mozilla\Firefox\Profiles
• *C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles
• Windows XP: C:\Documents and Settings\<user>\Application Data \Mozilla\Firefox\Profiles\

Search for the above file. Then rename or delete it. Restart Firefox.

The proposed solutions still do not work. I have uninstalled Firefox and cleaned the registry reboot my pc and reinstall Firefox 82.0.2 x64 bit it still doesn't work.

I called for more help.

I come back to you my problem is not solved if anyone can help me thank you