When I try to enter a prolongation dot by typing the period key on my numeric keypad (part of an older Apple USB keyboard), nothing happens in Dorico. When I use the period key on the main keyboard it’s fine. I have no similar problem in any other program. Using latest Dorico version and OSX 10.11.6. Looks like a bug?
No, it’s not a bug: the dot key on the numeric keypad is not assigned as a key command, but you can add it yourself if you like. Go to the Key Commands page of Preferences, and choose NoteInput > Dotted Notes from the list of commands on the left. Click in the ‘New key command’ field and type the dot on your keypad, which will show up as Num+. in the list. That should do it.