This error usually indicates that you are successfully connecting to your SAN target, but the SAN disk you are trying to access does not exist.
Things you can try:
Check the
ACL settings on your SAN target to ensure that the iPXE initiator will be granted access to the SAN disk. Many SAN targets will allow you to restrict the visibility of individual SAN disks on the basis of the initiator's identity (e.g. the iSCSI initiator IQN). If you are using an iSCSI target, see also
error 0x2c0d603b for iSCSI-specific information relating to ACLs.
Check the LUN mappings on your SAN target, and make sure that iPXE is attempting to connect to the correct LUN. If no LUN is explicitly specified, iPXE will connect to LUN 0, which may not be correct for your setup. For example, if your iSCSI root path is
iscsi:iscsi.example.com::::iqn.1992-01.com.example.iscsi:target
then iPXE will connect to LUN 0, since no LUN is explicitly specified. To instruct iPXE to connect to LUN 1, you would need to use an iSCSI root path such as
iscsi:iscsi.example.com:::1:iqn.1992-01.com.example.iscsi:target
^
\_ LUN goes here