If SYNCHRO 4D Pro is consistently crashing on startup, you can try cleaning the SYNCHRO Registry folders.

Warning: Be careful when editing the Registry, or you may damage your Windows installation. Modify or Delete only the keys as described below

1. Make sure you have closed SYNCHRO 4D Pro and saved any necessary files.
2. In your Start menu type regedit & click on regedit to open the Registry Editor.
   
   
   
3. Inside of the Registry Editor expand HKEY_CURRENT_USER.
   
   
4. Inside HKEY_CURRENT_USER, expand Software.
   
   
   
5. Inside Software expand the Synchro folder.
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6. Delete the following:
   a. HKEY_CURRENT_USER\Software\Synchro\Synchro\Default Layout State
   b. HKEY_CURRENT_USER\Software\Synchro\Synchro\GUI Layout x (x can be 1-4)
   c. HKEY_CURRENT_USER\Software\Synchro\Synchro\Settings
   
   
   
7. Open HKEY_CURRENT_USER\Software\Synchro\Synchro\ProjectConfig.
8. Delete everything in ProjectConfig EXCEPT
   a. (Default)
   b. Anything starting with FNL (deleting these keys may remove your license information)
   
   
   
9. Close the Registry Editor & re-open SYNCHRO 4D Pro.
10. If the problem persists, delete the whole Synchro folder.
    

If cleaning the registry doesn't help, do the following as well - 

1. Change this folder name:  C:\Users\username\AppData\Roaming\synchrohub <--- change to oldsynchrohub or delete
   
2. Run the attached program first, and then reinstall the appropriate SYNCHRO Pro/4D Pro application
   4812.SynchroInstallerHelper.7z