I have some issues with turnserver

Good morning everybody,
i am on internship in a company that uses nextcloud in order to allow sharing files and visioconference through this technology.
But when we wan to use visioconference outside our network, it is not possible and i found that a turn/stun server was neeeded.
I followed the instructions of the link below (i didn’t use tls certificate) and dedicated one public IP for this server :

when i run a test on my nextcloud server. it display that my settings have been well done.

when i try a video call, i get a black screen with ?.

My questions are :
How can i solve it ?
Do i need another server ?
Here are the logs i get :
270: session 001000000000000002: TCP socket closed remotely
270: session 001000000000000002: closed (2nd stage), user <> realm <name_server> origin <>, local, remote, reason: TCP connection closed by client (callback)