Unable to hear caller's on my LAN

I installed FreePBX everything installed with no error or warning
and i create 2 extension i can’t hear caller’s
i don’t have external line i’m just have local extension in my local (LAN) so i don’t have NAT

i check the speakers and microphone there is no problems
so please please help my


does the extension ring when you dial it? can you hear anything if you dial voice mail? are the phones actually registered with the pbx? which version of freepbx? what type of phones? what do the network settings look like?