Can't see or hear other users (and they can't see or hear me)

Hi I’ve (after quite a few trys) managed to install Jitsi meet on a VPS running Debian 9 with 8Gb of memory and 4 cores.
When I start a meeting, people I invite appear on my screen but we can’t hear or see each other, just a square with the name of the person in it.

From reading around I’m assuming ports are the problem and although ufw shows that the necessary ports are allowed as shown below

Status: active
To Action From
– ------ ----
22 ALLOW Anywhere
80/tcp ALLOW Anywhere
443/tcp ALLOW Anywhere
4443/tcp ALLOW Anywhere
8443/tcp ALLOW Anywhere
10000:20000/udp ALLOW Anywhere
22 (v6) ALLOW Anywhere (v6)
80/tcp (v6) ALLOW Anywhere (v6)
443/tcp (v6) ALLOW Anywhere (v6)
4443/tcp (v6) ALLOW Anywhere (v6)
8443/tcp (v6) ALLOW Anywhere (v6)
10000:20000/udp (v6) ALLOW Anywhere (v6)

When I test the ports with nmap, it shows that the ports aren’t actually open

Starting Nmap 7.40 ( https://nmap.org ) at 2020-05-11 18:27 UTC
Nmap scan report for (77.68.118.165)
Host is up (0.0000090s latency).
Not shown: 983 closed ports
PORT STATE SERVICE
21/tcp open ftp
22/tcp open ssh
25/tcp open smtp
53/tcp open domain
80/tcp open http
106/tcp open pop3pw
110/tcp open pop3
143/tcp open imap
443/tcp open https
465/tcp open smtps
993/tcp open imaps
995/tcp open pop3s
5222/tcp open xmpp-client
5269/tcp open xmpp-server
5280/tcp open xmpp-bosh
8443/tcp open https-alt
8888/tcp open sun-answerbook

I assume that this is the problem, but I don’t know how to fix it. I’m very new to all this, so I apologise if this should be obvious. Any help gratefully received.
I have looked up similar topics but they don’t quite seem to me to match my problem. Thanks in advance to anyone that answers.