Why don't the default Agent Login and Logout Postfixes work on Grandstream Call Queues

Issue:
When creating a Call Queue your Agents are unable to Login and Logout of the queue using the default Postfix. 

Resolution:
If you are trying to use the default Login and Logout Postfixes (i.e. 6500* to login and 6500** to logout) the call will fail from a Grandstream IP Phone with the default Dial Plan.




Step 1:
Login to your UCM61xx and setup a Call Queue if you haven't already:

Step 2:
Make sure you have configured the Agent Login Settings as per below:

Step 3:
If using Grandstream IP Phones that are provisioned via Zero Config you can add the following to the Global Policy:
After you have enabled the Dial Plan globally ensure you update / re-provision all phones so they receive the updated Dial Plan.

Step 4:
From one of the phones try the following:
Login to Call Queue 6500: dial 6500*
Logout of Call Queue 6500: dial 6500**