first stop the coturn.service using sudo systemctl stop coturn then use live watching the logs using sudo turnserver -c /etc/coturn/turnserver.conf -v so next from other linux client test your turn server to work successfully by:

turnutils_uclient -v -u username1 -w key1 -r your.realm.com turnserver_pub_ip

Also to test that the port is open or not use this:

1. For TCP ports: nc -zv -u turnserver_pub_ip 3478

2. For UDP ports: nc -zu -u turnserver_pub_ip 65535