Are you talking about Spreed.ME with dedicated spreed server or the “new” spreed video calls/talks app?
In both cases coturn and spreed server/app need to be configured. See this guide a bid down the first post for Spreed.ME and coturn configuration: Complete NC installation on Debian with Spreed.me and TURN step by step
For the “new” app, giving coturn domain:port as STUN+TURN server within apps settings should be enough.
Note that the app does not work in combination with http/2, which will be fixed with NC13 release. The app name is changed to “talks” there, if I saw right.
In case post turn server + app settings for further investigation. Coturn port also forwarded to from router to server in case? 