Create Drum Map from Instruments (GA5) - grayed out?

I had used this feature before, but for some reason now “Create Drum Map From Instrument” is grayed out.

Using with Groove Agent 5 pro as Instrument Track

Windows 7,

Cubase 10.0.6

Works here, although different Cubase & Windows versions. There is a limitation on that function where if you use it to create a map then it will be greyed out if you try to create a second map on that Track.