Hi,
I also had some problems to configure this SIP part correctly, however I am an IP phone operator.....
First of all, forget about IPTEL completely, it doesn't work/no longer works.
On the other hand, it works perfectly with ANTISIP.
Here are some quick elements that should help you, if necessary I'll take screenshots but now I'm in a bit of a hurry.
1/ First configure the SIP module of the intercom from its WEB portal, when you validate, the module restarts.
(from memory when you confirm the settings, the intercom restarts, emits beeps and the light flashes and then remains fixed green, if nothing happens to your intercom it is because there is a problem)
2/ In the Loxone Config, add the Video intercom and associate the asset with the SIP intercom as in their procedure:
/!\ In the network settings, I noticed that Loxone config was filling in gateway and DNS settings that are not good, checked twice before validating.
and that's all in principle.