Shared Room (Resources) Mailbox Calendar on iPhone

Hi guys,

I think I've hit a brick wall with this one. I have two test accounts in Microsoft Exchange called "Tiger" and "Zebra". They are both connected to a Room (Resources) Mailbox called "RoomTest". In Outlook 2010 on Windows 10 I can see the calendar perfectly as both accounts, and adding the room bookings works as expected.

Now the problem is when I try to use the calendar in iOS, when I add an Exchange account, in this case "Zebra", to the client's iPhone they can see the calendar for "Zebra" but not the shared room calendar called "RoomTest".

Does anyone know how to get this to work?