When a TeamCity configuration is created there are requirements the TeamCity Agent has to meet.
The creator of the build configuration can specify Explicit Requirements on the Agent Requirements page of the Build Configuration Settings.
When the build configuration is created, TeamCity automatically adds Build Step Requirements.
The bottom of the same page shows the list of compatible and incompatible agents.
If you visit the incompatible agent, most likely it will not contain the parameter, or the value will be different from the requirement. To see the expected value of the parameter, open the Agent Parameters, Configuration Parameters tab of an agent that satisfies the requirement.