Virtual Desktop Pool not showing in RDWeb Access

Hi All,

I follow a microsoft technet guide on deploying Managed Virtual Pool, my setup as following:-

1 x RDVH server

1 x RDWA Server

1 x RDCB Server

2 x Windows 8 Client Sysprep Image

I have completed the setup but when i login through Web Access, I cannot see the Virtual Desktop Pool. But i can assign remote APP such as calculator, paint and so on.
After further investigation, i found out that under the Virtual Desktop Collection. The Show in RD Web Access is set to No. It is in grey mode which I cannot change to Yes. Anyone can advise what could go wrong? How to enable the Virtual Desktop Pool in Web Access?

Thank you.