Hi Alpesh,
It looks like your devices are not registering correctly, so the call is droping when you dial the extension. If you are using Zoiper see this tutorial:
https://www.ringroost.com/blog/registering-a-zoiper-softphone-with-ringroost/
If you are still unable to get devices to register, let us know a time (mon-fri/9-5) that we can schedule remote session to help you get setup.
Thanks,
RingRoost Support Team