You may try and have them download the latest version, here are the links: 

macOS: Download

Windows: Download 

We can try a clean reinstall to further our troubleshooting, steps below: 

1. Uninstall the app using the uninstaller: Go to Add or Remove Programs in Windows (the exact UI differs for Windows 7 and Windows 10), search for ReachUC and uninstall it. 

2. In File Explorer, go to %LocalAppData% (just type this in the address bar) and delete the folder named reachuc-updater if it exists. 

3. In File Explorer, go to %LocalAppData%\Programs and delete the folder named ReachUC if it exists. 

4. In File Explorer, go to %AppData% and delete the folder named ReachUC if it exists. 

5. In File Explorer, go to %ProgramFiles% and delete the folder named ReachUC if it exists. 

6. Reboot the system and log in to the same user again. 

7. Reinstall the app from the link provided above.