Cannot use Remote Desktop Services Farm as a RemoteApp Source

I am having difficulty using a farm as a RemoteApp source on my RemoteApp Connection Broker. When the farm is specified as the RemoteApp source on my Connection Broker, no RemoteApp Programs populate in RD Web Access.

If I specify one of the Session Hosts as the RemoteApp source then the RemoteApp Programs list will populate as expected.

Any suggestions as to what I can check would be greatly appreciated.

Edit, more information:

I should also point out that, for the purpose of testing, there is only one Session Host. This Session Host is on the same server as the Connection Broker.

The Connection Broker is called farm02.domain.com and the farm name is farm.domain.com.

The error that occurs is:

Access to the WMI interface on Remote Desktop Session Host server farm.domain.com was denied. Add the Remote App and Desktop Management computer to the TS Web Access Computers security group on farm.domain.com

Error Code: 0x80070005

This error suggests I should add the Connection Broker/Session Host computer to its own TS Web Access group, which I have already done without resolving the issue.

Regards,
Nick Friday