@Abia Samuel, Thanks for posting in Q&A. From your description, I know 100 of 300 devices are not compliant because "has a compliance policy assigned". But for these devices, we have created compliance policy for them. Based as I know, I wonder it can be that it still needs some time to let the compliance status to change. And it can happen at next check in. Please wait for 8 hours to see if the status will be changed.
However, if the status still not changed, it can be some problem in the background. Please open case to fix the issue. Here is a link with the steps to open case.
https://learn.microsoft.com/en-us/mem/get-support
Hope the above information can help.
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