Users can't see Whiteboard button

I recently got the whiteboard to work with this guide:

Now I’m facing a rather small problem but it annoys me quite a bit. I’ve configured a secure domain for my instance. When I open a room and another person enters it, the whiteboard button is not visible until I (the moderator) open it first.
Is there a way to make the whiteboard visible for all users by default? It works like that on meet.jit.si. My guess is that is has to do with the secure domain.

Everyone on meet.jit.si is a moderator, that’s the difference. A whiteboard can be started only by a moderator.