Why can’t I make a failover cluster using iSCSI for shared storage

I’m trying to build a 2-node failover cluster (sqlnode-1, sqlnode-02) using Server 2016 guest VMs in my Hyper-V-based lab.

The problem I have is that the cluster wizard doesn’t recognise my shared storage.

I’m trying to use iSCSI for the shared storage. I’ve attached a new VHD to a third VM, mounted as Z:, and setup the following virtual disks on it to use for the quorum and shared storage:

I can connect this this from sqlnode-01:

I can only connect to it from sqlnode-02 if I first disconnect from sqlnode-01.

Is this expected behaviour or should I be able to connect from both at the same time? – And see the storage from Computer Management on both servers at the same time?

If I use the validation checker from Failover Cluster Manager I see the following:

All following tests are Not Applicable – presumably as it hasn’t found any disks to be validated.
I get the same results whether I’ve left the disks offline or brought them online.

Is there something obvious I might have missed when setting up the iSCSI target?

The validation report states:

Physical disk {82996b53-d867-4086-993c-7813c8f5e154} is visible from
only one node and will not be tested. Validation requires that the
disk be visible from at least two nodes. The disk is reported as
visible at node: sqlnode-01.corp.local