Below is my Mango Dashboard Admin Template URL -
In the above page there is one option for "Click here to View the admin template" then below page is opening.
This page is not loaded fully. That is only index.html file is showing the loading image. the content page , i.e., the home page is not getting loaded.
In version 2, it was opening though.
I have also tried to copy the entire folder structure to the override folder and kept it as described in help page of Mango Dashboard v3. But page link is saying broken.