And why is that? Have you not enabled the codec on FreePBX? Also, there’s no video support over the PSTN so the video calls would only work extension to extension.
Your phones are perfectly capable of video calling with FreePBX.
In order to enable video in Asterisk, add the following variable to your SIP configuration, under the general section:
[general]
…
…
…
videosupport=yes
Then for each SIP user / peer, you have to add the supported codecs. Depending on your Asterisk version, you might want to avoid video codec negociation, so make sure that you enable a single video codec. Also, reinvite=no might be needed, if you have reinvite=yes and the video is not coming up, try setting it to no.
You should be able to see video codecs when you enable Video Support, otherwise they will not be shown. If you are using CHAN_SIP, then you need to go to “Settings” → “Asterisk SIP Settings” → “Chan SIP Settings”, then set “Video Support” to “Enabled” and you will be presented with a list of available video codecs. If you are not using CHAN_SIP but CHAN_PJSIP, you should perform a similar process, but I’m not sure about it as I don’t use CHAN_PJSIP.