So, this was a frustratingly easy fix that took me about 20 minutes figure out. I was patching a customers HyperV Clustered servers but found that one server failed to migrate to a different clustered node, when I tried to Drain the Roles.
I tried to migrate the server manually, but as you can see in the screenshot below it still failed:
Event ID 21502 'Virtual Machine SRV-FS6' failed to start. 'SRV-FS6' failed to start. (Virtual machine ID A1AD28F5-C3BD-4882-9426-FAF65BD4A30) 'SRV-FS6' Synthetic SCSI Controller (Instance ID 2B9B1504-3BF7-4600-BE1F-F570BF15C61C): Failed to Power on with Error 'General access denied error' (0x80070005). (Virtual machine ID A1AD28F5-C3BD-4882-9426-FAF605BD4A30) 'SRV-FS6': The Machine Account 'URTECH\SRV-HV02$' does not have read access to file share '\srv-hv01\c$\Temp\17763.3650.221105-1748.rs5_release_svc_refresh_SERVER_EVAL_x64FRE_en-us.iso'. Please add this machine account to the file share security group. Error: 'General access denied error' (0x80070005). (Virtual machine ID A1AD28F5-C3BD-4882-9426-FAF65BD4A30)
Clustered VM Error Event ID 1205 VM Will Not Migrate One or More Resources May Be In A Failed State
The error message on event id 21502 was actually pretty clear. It told us that the other clustered node did not have read access to an ISO that was recently used on that server. The fix was either to grant read permission on that file or you could do what we did and just eject the disk, which disconnected the ISO.
Once the ISO ‘DVD’ was ejected, the virtual machine was able to move without problem to a different clustered node.