Please consider turning on send info to Mozilla before posting a question. This helps us help you. As I have no info from your system that would help see things that cause issues.

Suggest Uninstall and reinstall Version 56.0.2 with the Full Version Installer. https://www.mozilla.org/firefox/all/

To cleanup any errors in Windows 10 do this please : Repair System Registry and Files

(FOR DOING Above & Below - WINDOWS All OTHER VERSIONS - Use Search To Find Command Prompt ** Enter CMD.exe to Find COMMAND PROMPT Then Right Click & RUN AS ADMIN)

To run the SFC command use the Windows key + X keyboard shortcut to open the Power User menu and select Command Prompt (Admin). Type "SFC /SCANNOW" (without quotes or copy/paste) and press Enter. For more information on using SFC, please refer to the Microsoft KB: Use the System File Checker tool to repair missing or corrupted system files

Run the Windows Deployment Image Servicing and Management (DISM) and System File Checker (SFC) tools as Administrator. The DISM and SFC tools scan the integrity of the Windows image and all protected system files replaces corrupted, damaged and incorrect versions. (FOR DOING Above & Below - WINDOWS All OTHER VERSIONS - Use Search To Find Command Prompt ** Enter CMD.exe to Find COMMAND PROMPT Then Right Click & RUN AS ADMIN) Type "DISM /Online /Cleanup-Image /RestoreHealth" (without quotes or copy/paste) and press Enter.

Windows 10 To run the DISM command use the Windows key + X keyboard shortcut to open the Power User menu, then select Command Prompt (Admin). Type "DISM /Online /Cleanup-Image /RestoreHealth" (without quotes or copy/paste) and press Enter. While running DISM you may notice the process will appear to pause at 20%. After a few minutes the operation will continue.

Note : SFC fixes files locally using files found on your system. Note : DISM goes up to Microsoft for new ones.

Note : Firefox 57 Quantum release date Nov 14th https://www.mozilla.org/en-US/firefox/quantum/ Note : Legacy Extensions will be disabled and or removed.

Please let us know if this solved your issue or if need further assistance.

I don't know what the Windows 10 Troubleshooter does, but if it says that Firefox is not compatible with Windows 10, perhaps there is a problem with the program files because Firefox definitely is compatible with Windows 10.

Hopefully the above system maintenance tips will be helpful. Here's one other thing to consider:

One of the main effects of the Firefox 56.0.1 update was to migrate 64-bit Windows users from the traditional 32-bit version of Firefox to the 64-bit version. We've received a number of puzzling reports of Firefox either not starting (probably due to incompatibilities with 64-bit drivers that Firefox expects/requires) or not loading any pages after this migration.

One user discovered that Windows was silently killing Firefox at startup and recording it in the Windows event logs (you can view event logs using the Event Viewer). Based on one of the reports in the log, we were able to trace that to an out-of-date Logitech camera driver, of all things. Two other users reported that uninstalling the Logitech camera resolved their problem as well.

• https://support.mozilla.org/questions/1179822#answer-1019375
• https://support.mozilla.org/questions/1181740#answer-1021470
• https://support.mozilla.org/questions/1181405#answer-1022798

Do you want some assistance in looking at event logs, or do you have such a camera?

If the investigation doesn't yield any solutions, it is worth trying a return to 32-bit Firefox.

While normally this kind of change is seamless -- the installer detects your existing data and preserves everything -- you might want to make a backup "just in case."

• Back up and restore information in Firefox profiles
• How to opt out of 32-bit Firefox migration to 64-bit

Note: If you decide to try 64-bit Firefox on the same system at some point in the future, see: How to switch from 32-bit to 64-bit Firefox.

thank you very much jscher2000 , I uninstalled my ageing Logitech camera and its software and FireFox started.. many thanks.