This is missing almost anything for someone to help you troubleshoot. You don't mentioned what MDM you're using, or anything that you've actually done to try and troubleshoot the issue.
If I had to take a wild guess with the information supplied, verify that you're actually allowing the DNS traffic from your clients to wherever your MDM is attempting to send the traffic.
As @BPry mentioned there is no info to investigate. My wild suggestion will be the HIP profile check that the devices are matching after the MDM is enabled so do a security policy trace https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA10g000000Cla1CAC , https://docs.paloaltonetworks.com/globalprotect/9-1/globalprotect-admin/mobile-endpoint-management/s...
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