Management Portal and IIS

When accessing management portal through IIS the page is not fully rendered and the buttons/links that are displayed don't work.

Management Portal works fine through private web-server.

Have just set up IIS/CSP Gateway to access Ensemble, and accessing the CSP Gateway configuration pages through IIS works fine (screenshot at end of post).

This is the view when accessing management portal through IIS (port 80) - missing images, links don't work, not all content displayed:

And this is the (top of the) view when accessing through the PWS (port 57772):

I've been following @Kyle Baxter 's helpful tutorial from YouTube: Configuring a Web Server for IIS for Better Performance and Security

This behaviour is the same in both Edge and Chrome.

Any pointers on diagnosing what is going on and suggestions for fixes welcome!

For reference, here is the CSP / Web Gateway Management page through IIS - looks like it is displaying fine: