Are you using Cloud Sync in WorkingHours?
Can you also please share:
- device model
- Windows region/language settings
- whether Windows had an update shortly before this started
Please also check what error is logged in Windows Event Viewer:
Open the Windows “Event Viewer” app, then go to “Windows Logs” → “Application” and look for an error entry from the time when you tried to start WorkingHours. Please copy the full error text here, especially the “Exception Info” / “Faulting application” details.
Please don’t use the “Reset” function or uninstall the app before you have a backup of the database, unless you are using Cloud Sync. The database file location is documented in the FAQ here