Cannot select RDS deployment - Session-based desktop deployment

Hi,

I'm trying to install RDS in a Session-based deployment, but this option is greyed out. I'm trying to setup a pilot server as RDS in Server 2012 is fairly new to us.

I start the RDS role installation the usual way:
-Add role or feature
-RDS install
-Select the existing connection broker in our organization. This was previously setup by a colleague and I can't vouch for it
-Choose Standard deployment....
and now the only choice I have is the virtual machine-based deployment.

When I try via. Powershell, I get the following:
New-SessionDeployment -ConnectionBroker adfs01.company.com -SessionHost corpsched02.company.com
New-SessionDeployment : A session-based desktop deployment is already present.
At line:1 char:1
+ New-SessionDeployment -ConnectionBroker adfs01.company.com -SessionHost co ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [Write-Error], WriteErrorException
    + FullyQualifiedErrorId : Microsoft.PowerShell.Commands.WriteErrorException,New-SessionDeployment

Thanks in advance,
Greg