This may be caused by several problems.

mDNS conflicts

NDI uses the mDNS (Avahi daemon on Linux) to discover NDI sources. Live Transcoder in Docker already has avahi-daemon up, and another avahi-daemon on your host system can lead to a conflict. Stopping the service on your host system solves the issue. You can stop it with this command.

sudo systemctl stop avahi-daemon

This command prevents the startup of the daemon at boot.

sudo systemctl disable avahi-daemon

Stop and start your Live Transcoder container again.

Cloud-specific problems

• The Live Transcoder host instance is in a different VPC or subnet than your NDI source.
• Ports needed for NDI source discovery are closed in your cloud provider's firewall (Security Groups in AWS)