I have a KX-TDE100 with KX-NT366 phones, with two new phones at a remote site with a VPN connection between sites. The phones work in all ways, except cannot be heard on outgoing calls, intercom or CO calls. Outgoing audio from either speakerphone or handset does not work, although incoming audio is fine through both. They just act like the microphones don't work, but when connected at the PBX site, phones work fine.
It appears that it may be an internet VPN issue.
Any ideas about what to check? I am stumped.
Thanks in advance.

• Peer-to-peer calls between KX-NT300 series IP-PTs installed at different locations may not be possible
if packet communication cannot be established between the respective networks. In this case, you
need to configure the network settings (e.g., a VPN router when using an IP-VPN) to establish packet
communication