Semantic Error (SEM1232): The function '...' does not have an output parameter with the name '...'.

The code contains a function which contains an output formal parameter that is not defined in the prototype of the function.

This error may also be reported after you have deactivated EN/ENO: If you have deselected the EN/ENO feature in the 'Options' dialog ('Extras > Options | EN/ENO > EN/ENO Settings') although the ENO output is already connected in the code. In ST, the error appears immediately after confirming the 'Options' dialog. In FBD, the error appears when updating the respective block icon in the code ('Update Function/Function Block' context menu item).

Remedy:

In case of an outdated (user-defined) function, update the function in the code by right-clicking the block icon and selecting 'Update Function/Function Block' from the context menu.

If the error appeared after deactivating EN/ENO:

Activate the EN/ENO feature in the 'Options' dialog.
After confirming the 'Options' dialog, the error disappears immediately in ST. In FBD, you first have to update the respective block icon in the code ('Update Function/Function Block' context menu item) in order to eliminate the error
Keep EN/ENO activated, or
first disconnect the EN and ENO formal parameter and then deactivate EN/ENO again.