Solution
This error occurs because the PostgreSQLDatabase service is missing a password in the configuration file. The TestMonitor service is dependent on PostgreSQLDatabase, which causes this error to appear.
To verify if your PostgreSQLDatabase service is missing a password:
- In a text editor, open C:\ProgramData\National Instruments\Skyline\Config\PostgreSQLDatabase.json
- If a password is missing, the Postgres.Password and Postgres.ConnectionString fields will appear similar to below.

To resolve the issue, follow the steps in SystemLink TestMonitor Error: Password Authentication Failed. Although this article references a different error, the solution is the same.