3CX PBX

I'm connecting the 3CX-Android-Phone on my HTC Wildfire (Android 2.2) over VPN, so I can use the option "User Internal Server".
The registration-process worked fine but I can't call anyone. I can take calls from everyone in the company but when I dial a number and press on the green call-button nothing happens.
Has anyone an idea what the problem could be?

Could it be a Problem with the "small" display on the Wildfire?
It hast only a resolution of 320 × 240.

Because if I get a call I have two red buttons to reject the call and one green to take the call.
I don't know if this is normal but it looks quite strange...

I would be very grateful if anyone has a solution for my problem!

Is you phone on the list of supported (tested) devices? Are you using the latest release 3Cx phone? Does this happen when not using VPN, on 3G, on WiFi?

I just found it out. I had to enable the 3G-option, otherwise it won't make any calls.
Thanks anyway!

Greetings Stefan