Check the application Event Viewer, and if there’s an unhandled exception referencing SmartPosting do the following:

1. Locate and browse to your program path. See How to find data path and program path for instructions on finding your program path.
2. In the program path, rename the following files:
   • SmartPostingInterop.dll
   • SmartPostingService2019.exe
   • SmartPostingService2017.exe.config
3. Run a repair on the program. See How to run Repair.
4. Verify that Sage 50 is now able to open.