I dont recall seeing an error code 18 mentioned before, other numbers yes, but not 18.

Did you uninstall, then rename the old folder (I think this is so the Windows registry entries install clean) then reinstall?  personally, Id reboot the computer after the uninstall/rename portion before I reinstalled it, the instructions don't say to, but I always do.

https://proconnect.intuit.com/community/help-articles/help/uninstall-rename-and-reinstall-intuit-pro...