Item Planner - List of Values Contains No Entries

Hello,

I'm trying to enter a Planner for a given item, which is a Purchased Item type.

However in the 'General Planning' tab, field 'Planner' gives me the FRM-41830: List of Values contains no entries.

The Planners have been defined already:

Both the item and the planners are defined in the same organization.

Could someone point me what I should do?

Thanks in advance.