This is a short one: While you will find plenty of blogs how to configure a Windows 10 Kiosk Device, I was not able to find a very important information:
Where can I find Information, if starting an app within a multiple App Kiosk configuration fails. And it’s that simple:
Open Event Viewer and go to Microsoft\Windows\AppLocker, there you will find more Information about the process that fails to start:
Hope this helps 🙂
blog.hosebei.ch 
Just curious, how do you even open Event Viewer on an Intune Multi App Kiosk?
There’s no Run, no start menu, etc. available.
if you remove the kiosk profile from the device, you can then normally login and check the eventviewer.
You can also go to switch user and logon with an account which is device admin (like a global admin account). You will not have a locked desktop with this user.
In the start menu you will be missing stuff like “Settings” but when you click on the search icon, you will see a couple of pinned apps which also includes the Settings.
There are also some other options for troubleshooting, see: https://docs.microsoft.com/en-us/windows/configuration/kiosk-troubleshoot