If a computer, although present in SCCM with correct MAC address and present in a OS Deployment collection, is refusing to PXE boot (or reports there is nothing to install) try checking the following:
Delete the PC with the Resource ID NOT present in your OS deployment collection.
Now the PXE process will find the correct PC and you’re good to go..
If you do NOT find Duplicate names the PC MAC address might still be present more than once,
but with a different PC name!
To check which PC SCCM believes is trying to PXE Boot, open the SMSPXE.log with CMTrace
(??:\Microsoft Configuration Manager\Logs\SMSPXE.LOG)
Search for the MAC address and along the line you’ll see the following:
Go back to the SCCM Console and search in Devices for the ItemKey value (here 16799140)
(add the column field “Resource ID”)
And if you find a PC with that ID, you’ve found the rouge PC… In this case a miss-spelled PC name.
Checking settings for the miss-spelled Pc reveals the exact same MAC address.
Delete the rouge PC and try to PXE again.