Neither dock or bar appears on external monitor when I move an app to it How can I fix it? This just started recently.  I have a MacBook Pro 15 2018 16 GB ram 512 GB HD. The external monitor is a Dell 24 inch with a 3820 x 2160 resolution.

I use it primarily for Azure development. 
If I position Safari against the top the monitor, the bar does not appear. It stays on main screen.
I have a secondary monitor hooked up to my iMac, take a look at "System Preferences > Displays", does it match the screenshot I have attached?

You can move the blue rectangles (screens) by clicking and dragging to the desired position, the same applies to the "bar" at the top of the screen

Hope this helps