What home page are you getting instead of your desired home page? Sometimes the address points to a culprit such as an add-on.

Are you able to change the home page temporarily? What is mean is, after you update the setting, either on the Options page or using the "drag to house icon" method (see: How to set the home page), if you launch a new window using Ctrl+n, do you get your new home page.

If it works temporarily but you get the unwanted page again after exiting out and restarting Firefox, some reasons for that problem are covered in this article: How to fix preferences that won't save.

If you can't even change it temporarily, the problem might be a locked setting or add-on. More on that depending on the situation.

You can check for problems with preferences.

Delete possible user.js and numbered prefs-##.js files and rename/remove the prefs.js file to reset all prefs to the default value including prefs set via user.js and prefs that are no longer supported in current Firefox releases.

• http://kb.mozillazine.org/Preferences_not_saved
• http://kb.mozillazine.org/Resetting_preferences

You can use this button to go to the current Firefox profile folder:

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

Start Firefox in Safe Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Appearance
• Do NOT click the "Refresh Firefox" button on the Safe Mode start window

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

There is software like Advanced SystemCare with its Surfing Protection feature that can protect files in the Firefox profile folder against changes. If you have such software then check the settings or uninstall this software.