@Richkm Thanks for posting in our Q&A.
From the screen shot you provided, you have set "App to run in kiosk mode" to "store app". For store app, it is needed to enter the app URL that get from iTunes App store.
https://learn.microsoft.com/en-us/mem/intune/configuration/device-restrictions-ios#settings-apply-to-automated-device-enrollment-supervised-8
For "com.apple.mobilesafari", it is a bundle ID, so it is needed to set "App to run in kiosk mode" to "Built-In App".
Hope it will help.
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