Function module & is not active

What causes this issue?

The function module you just edited is inactive and cannot be used.

System Response

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

How to fix this error?

The function module must be activated before it can be called.
If this does not give you the required success, it could be that an old
function module exists that is based on the inactive procedure for
function modules prior to Release 4.5. This procedure was made obsolete
with Release 4.6. For activating this module, use the report
RS_FUNCTION_ACTIVATE_OLD.

Error message extract from SAP system. Copyright SAP SE.