Hi,
First of all, please run gpresult /h command to check if the GPO is applied successfully to clients.
If not, you could check the following article regarding 10 common problems causing group policy to not apply, you could try to check it one by one:
http://social.technet.microsoft.com/wiki/contents/articles/22457.10-common-problems-causing-group-policy-to-not-apply.aspx
And you could follow the article as below regarding Windows 10 Start Layout Customization via group policy and see if anything is different in your settings of GPO:
https://blogs.technet.microsoft.com/deploymentguys/2016/03/07/windows-10-start-layout-customization/
If the GPO is applied correctly, I am afraid that something wrong might happen on the XML configuration, in this case, I would suggest you post the question in the windows 10 forum to have a try if someone could offer help to analysis the file:
https://social.technet.microsoft.com/forums/en-us/home?forum=win10itprogeneral
The reason why we recommend posting appropriately is you will get the most qualified pool of respondents, and other partners who read the forums regularly can either share their knowledge or learn from your interaction with us. Thank you for your understanding.
Best regards,
Wendy
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