I just upgraded from 5.0.5 to 5.1.0, and the navbar just stops working, doesn't show any content inside of <mdb-navbar></mdb-navbar>.
After digging into the source code, I found in the navbar.component.html, it is missing <ng-content></ng-content> which exists on the 2nd line of version 5.0.5. So, I added this line and it starts working again.
Furthermore, there are two lines of<ng-content select="logo" ></ng-content>, shall I delete one?
I have the same problem. Definitely something wrong with the navbar.component.html having two logo content areas. It also seems like the examples for the standard navbar are inconsistent with the navbar section in the double-nav examples.