I may be off chart here, but it seems as if you try to add storage?
If you go to the storage adapters (on the second ESXi box), and select your iSCSI adapter (usually vmhba35), do you see any targets listed under "Details" on the bottom half of the screen?
Of so, the connection is perfectly fine, you should be able to see the storage you created for the first ESXi box when you click "Storage".
-> "Add Storage" is meant to create datastores, when we talk about shared LUNs, we talk about shared datastores. They only need to be created once ...