@Namless Shelter , From your description, it seems the iPhone is not powered on after 1 month and now it seems the device can't get Intune action and has error with compliance Policy.
Here, we suggest to firstly open company portal to sync the device with Intune to see if it can sync with Intune. Here is a link with more details for the reference:
https://learn.microsoft.com/en-us/troubleshoot/mem/intune/ios-devices-inactive
Please try the above suggestion and if there's any update, feel free to let us know.
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