no multiple docks?

Make the inactive screen active by either clicking on a window on said screen or on the upper bar.
dock should appear then (or pop up on the bottom half if you auto-hide it)

 

Seems very buggy or inconsistent to say the least.
Takes me serveral attempts of clicking on the secondary screen (either background or top bar) until finally the Dock sometimes pops ups (I have it on auto-hide though)

 

The threshold for activating the dock when hidden seems to be very high on the secondary display. In order to activate the dock on the secondary display I need to mouse down to it and then keep mousing down against the screen frame to activate it. Once the dock has appeared on the second screen then it activates again fairly easily there, but to activate it on the primary screen I need to go through the same ritual.

As someone who only plans to use the dock on the primary screen, I don't mind this behavior. It ensures that I won't accidentally activate the dock on the secondary screen. I can imagine why it would be a hassle if you plan to use the dock regularly across both screens, though. It seems that Apple could easily fix this by offering a series of settings (keep dock on primary screen or allow it to freely activate on both screens), but their aversion to user settings and customizations leads them to implement compromises like this.

 

For me it sometimes just disappears and only switching to a different space on the same screen, go down to the dock and back makes it reappear.
It is some bug. I wrote Apple a bug report.

It doesn't seem to work too well. I don't use it much so I don't care all that much.