Problems with nextcloud talk

hello I have a problem with calling via nextcloud talk, I have ubuntu server 20.04 installed and I have nexcloud set up there completely. I have nextcloud talk installed on my android phones and when I call it it rings me but the other party does not see that someone is calling. it’s on the local network

Looks like that you don’t have a STUN server

yes I don’t have STUN, I thought that when I install it, I will configure it so that I can do it within the LAN