If you have been building Windows OS with SCCM then you know that Computer Association can be a pain in one place 🙂 Here are several things to be checked:
1. Check Unprovisioned Computers folder for the records on the SCCM server where you did association. Delete the record and retry Computer Association.
2. If your SCCM server has a Parent then you need to run SCCM console on the Parent site server and check for Unprovisioned Computers there as well. Delete the record and retry Computer Association.
3. Check for the same MAC address and Computer Name in SCCM database. There is a chance that there is an object with the same MAC or Name. This can be done using SCCM Reports. SQL query below finds computers with 00:15:4C:0B:1C:05 MAC address:
SELECT NETW.DNSHostName0, Netcard.MACAddress0, NETW.IPAddress0 FROM v_GS_NETWORK_ADAPTER Netcard JOIN v_Network_DATA_Serialized NETW on Netcard.ResourceID=NETW.ResourceID and Netcard.MACAddress0=NETW.MACAddress0 WHERE Netcard.MACAddress0 LIKE '%00:15:4C:0B:1C:05%' ORDER BY Netcard.MACAddress0