@Mohamed Umer, Thanks for posting in Q&A. From your description, I know the PowerShell Script to change desktop background image is not working until the device is unenrolled from Intune. If there's any misunderstanding, feel free to let us know.
It seems the script has been deployed successfully and the registry key for desktop backgorund image has been changed in the registry key. But it doesn't take effect although we restart the device.
to Clarify our issue, please collect the following information:
- For the affected user, if we login other devices, did it have the same result?
- What is the status of the PowerShell script in Intune portal for the affected device?
- How many devices are affected? Did it affect all? Is there any difference between the working one and not working one?
- Was there any other policy or script assigned to the same user and same device which also set desktop background image?
Please check the above information and if there's any update, feel free to let us know.
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