Firstly, it is worth ensuring you are attached to the correct process. Some applications have multiple process threads running in task manager and connecting to the correct one is important to be able to interface with it.
WPF is a new type of application and product changes were required to be able to interface with them. Checking the Blue Prism release notes I can see that version 5.0.23 has a change item that says ""Blue Prism is now certified for installation on Windows 10. This includes support for launching and
spying ""Windows Apps"" provided in Windows 10.""
I would therefore suggest that you need Blue Prism 5.0.23 if you want to interface with these kind of apps.
Beyond that, your get out of jail is to use Surface Automation techniques - which are a lot easier to use robustly in version 6. Also, a new release of v6 expected over the next few months will include a new Microsoft UIA interface that may improve the interface options with these kind of apps.