Hi,
Thanks for posting in Microsoft MECM Q&A forum.
1,For UEFI mode, please ensure that your Disk Type is set to GPT not MBR. Also make sure the Swith or Router will not block the broadcasting of the UEFI booting. Refer to:which was blocking the broadcasting of the UEFI booting
Note: This is non-Microsoft link, just for your reference.
2,We can also review the BDD.log and SMSTS.log on the client to see if there is any further information for troubleshooting.
Best regards,
Simon
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