The next step would be to check your routing on the voice vlan.
You'll need to check you DFG and mask.
But...
Can I assume that it's only the console with the issue? All other phones work fine? That would suggest the DFG and mask are correct.
There's a couple of test you can do.
At the far end, find a 5330/5340 or 5360. Hold the UP&DN volume buttons, release the down button and dial 234 then release the up arrow.
Say 'no' until you get to "tools and features" then say 'no' until you get to ping test. - Say 'yes'.
Enter the IP address of your console keypad - Note: this is not the PC IP address. The keypad has it's own.
(You may have to look in your DHCP server to find out what the address is.)
Ping your keypad. It should ping it 5 times and either fail or pass. This will test to the keypad.
Now, since you can hear them but they can't hear you, it would look like the issue is on your end so the above test wont tell you too much -unless it fails -
There isn't a way to test from your keypad outbound this way. You may have to manually set up a 53xx phone manually with the same IP address as your keypad and test that way - 1st with a call and then with a ping. Remember to disconnect your keypad 1st before setting up a phone this way.
Ralph