Issue when connecting to desktops from appportal

Hi, we are currently doing a POC on VDI for one of our customers. Due to the above mentioned issue we are unable to proceed. Hence would appreciate if you could provide us a solution asap.

The active directory and DNS of our customer are located in the same server which runs on Windows Server 2008 R2 version. The server version of our connection broker is Windows 2012 R2. Connection broker and the client machines are of two different ip ranges. We have done the initial setup and encountered no issue with the connectivity between them. We have installed Appportal to client machines and we can access the allocated desktops through the Appportal from Domain Admin. But when we try to connect to the desktops from domain users, it triggers the below error:

“To log on to this remote computer, you must be granted the Allow logon through terminal Services right. By default, members of Remote Desktop Users group have this right. If you are not a member of the Remote Desktop Users group or another group that has this right, or if the Remote Desktop users group does not have this right, you must be granted this right manually.”

Initially I thought it is an issue with the user rights, hence I allocated the users to the remote desktop user group and also added a group policy through local group policy editor. But still the error keeps on appearing. And also I tried to RDP the desktops from client machine. Then I realized that this issue appears with certain desktops only. For example: I created 5 desktops in the desktop group. For two of them any domain user could log in successfully through Appportal. But for rest of the three desktops, any of the domain users couldn’t login. The IPs are assigned to the desktops through DHCP. But I assigned static IPs and tried to login. But still it fails. I would really appreciate if you could assist me on this issue. Thanks in advance