"cant hear person calling in"
"Person calling can't hear me"
Check first - Is headset default in and out device?
if:
No - make sure headset plugged in - Mic not muted and 3CX Sees it as default in/out audio device.
Yes - Check WaveMaxx audio - Stop it from running in TM, Disable as a startup item, uninstall if possible
If you disable WavesMaxx - test the headset, if you can hear other sounds through it (youtube, system sounds etc)
but 3CX is still silent, go to settings > Scroll to Audio Options > Make sure "Microphone" "Speaker" and "Ringer" are all set to Jabra headset.
Make sure "Headset" button is checked.
This should resolve any issue with 3CX Sounds.