I'm having a problem with the 3cx and the devices on the internal network. My server is on the local network, and I have 3 devices, 2 Fanvil X4 and a Yealink T-48. I'm having the error when I call an extension it goes to mailbox and the error appears: has failed; Cause: 487 Request Terminated / INVITE from ...... The devices have already been reset and reprovisioned. In addition they are not with DND on. Is anyone experiencing this problem?