I have Brian Lagunas demo code working with PRISM 6 and Telerik controls.
It seems the problem was in the parameters being pass during navigation.
Use of Telerik controls was not in error.
The solution is posted at https://github.com/spaceradars/ignavtelerikfix
The name of the solution zip file is
igoutlookUnity5 Implementing Navigation and a little MVVM.zip
The solution posted corresponds to video Building IG Outlook Part 5 - Implementing Navigation and a little MVVM,
There are two more videos Part 6 and Part 7 I need to watch to get a full work solution.
Thanks for all you help.