SAP Note 12487 - GPA/SPA user parameters not set

Symptom:
User parameter IDs exist for some fields, but they cannot be set with "System -> User profile -> User parameters".
Cause and prerequisites

Fetching of user parameters from the parameter pool or setting of parameters in the parameter pool must be explicitly programmed or accessed in the screen. Therefore, the parameters that are set do not automatically apply to all transactions. Example: Business areas (GSB) are not set for FI postings.

To determine whether parameter values have been set in the standard system, use SE51 to check the attributes (SPA/GPA) of the relevant screen field to see if it is active; then check the PBO (process before output) module in the flow logic to see whether "GET PARAMETER ID..." has been explicitly programmed.

Solution
See Cause