Ofmeet - error org.jitsi.impl.neomedia.transform.dtls.DatagramTransportImpl is closed!

when other partecipants login have done in video-meet, i can’t see them. I see new people in the room but the screen is black. In the file log apper this error:

org.jitsi.impl.neomedia.transform.dtls.DatagramTransportImpl is closed!

Openfire 4.1.1, ofmeet 0.3.28

thanks

Gigi