The function 'Activation Personnel Assignment' is not available

What causes this issue?

No active implementation was found for the HRPAD00MGEACTIVATION
Business Add-In.

System Response

The activation cannot be performed.

How to fix this error?

Activate the implementation for the Business Add-In delivered by SAP or
activate your own implementation.

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.