Your error log shows that something is blocking access to the GSX own cache folder:
got error CreateFile failed: The process cannot access the file because it is being used by another process: "C:\ProgramData\Virtuali/Couatl/prepar3dv4\files.bin" (system:32), accessing "C:\ProgramData\Virtuali/Couatl/prepar3dv4\files.bin"
The offending program can possibly be the antivirus so, try to exclude the whole Addon Manager folder from scanning first.
If that doesn't work, try this:
- Reboot Windows
- REMOVE this folder "C:\ProgramData\Virtuali/Couatl/prepar3dv4", when the sim is NOT running
- Reinstall GSX