The workstation and server aren't running the same Sage 100 Contractor release version.
The workstation program is upgraded while the server isn't, or the server database is upgraded while the workstation program isn't.

Solution overview

Verify the release version on the server matches the release version on the workstation.
Confirm that all databases are upgraded on the server.
Reinstall or upgrade as needed when versions differ.

Verify matching release versions

Check the release version in Database Administration for Sage 100 Contractor.
Look for the white text on the black header.
Confirm it matches the release version in the Sage 100 Contractor program inside the Home & Resources tab, About Sage 100 Contractor.
Access the Home & Resources tab by clicking the tiny X in the Connect to SQL Server login box when you open the company.

If the release versions match, go to the next section.
If the release versions differ, upgrade the server and all workstations to the same release version, or uninstall the workstation running the higher version and reinstall the matching server release.

Confirm all databases are upgraded

1. Open Database Administration for Sage 100 Contractor on the server.
2. Choose Upgrade Company Databases.
3. Choose the company.
4. Select Upgrade Databases.

If any databases are bolded, upgrade them.