Chat works, but no sound or video

So I have installed Jitsi on an AWS EC2 instance according to these instructions:

I’m able to create a meeting, I can see that other users are in the meeting, and chat is working fine, but there is no audio or video from other users. I can see what’s coming out of my own camera on screen.

What might be wrong here, and what can I do to debug it?

https://jitsi.org/qi advanced section.

Ok, so I have tried setting the NAT config values:

org.ice4j.ice.harvest.NAT_HARVESTER_LOCAL_ADDRESS=<ECS "private" IP>
org.ice4j.ice.harvest.NAT_HARVESTER_PUBLIC_ADDRESS=<public ip>

and removed org.ice4j.ice.harvest.STUN_MAPPING_HARVESTER_ADDRESSES

I’ve also tried setting the AWS harvester setting:

org.ice4j.ice.harvest.DISABLE_AWS_HARVESTER=false

as well as the values in /etc/systemd/system.conf

Now it appears to be working fine on Chrome, but it’s not working from Firefox or Safari. Is there anything I have done wrong or anything else I can try?

edit: also when any firefox browser is in the meeting, none of the video seems to work