As I recall I encountered this error in BBB 2.5.
Then here they gave me this solution:
Implementation:
chmod 755 /etc/bigbluebutton/bbb-webrtc-sfu
chown bigbluebotton:root /etc/bigbluebutton/bbb-webrtc-sfu
chmod 600 /etc/bigbluebutton/bbb-webrtc-sfu/production.yml
chown bigbluebutton:root /etc/bigbluebutton/bbb-webrtc-sfu/production.yml
bbb-conf --restart
sudo bbb-conf --status