Lack of response?

[ItzArty]

Hey, I have been programming for quite a long time but I probally will never be experienced to make something like this myself ever. Anyway I tried to set this up and got it working, but whenever I try to make a call, I can absolutely chat and things, even accept the call, but as I do anything, when accepting the call, nothing happens, the call seems not to start and even tho I clicked accept, the second side gets an error saying that there was lack of response from other side, what could this be caused by?
(It keeps saying setting your call up but nothing happens until the request times out)