Solving problems with video calls via the Talk app

Dear colleagues please forgive me for my ignorance but I need your help
After installing and configuring Nexcloud there was a need to make video calls for conferences but after installing the Talk app there were some problems when calling the interlocutor does not see me but I see it and the same problem with the sound
Nexcloud is installed via snap, I make calls inside the local network
during the call, a message pops up about the need to configure turn
As far as I know from the instructions I read turn is necessary for communication outside the local network