I haven't yet, as no issues with any other sites. What's strange is that it doesn't work from my Zen connection, nor through the wife's company network when she VPNs into them.
What does work is using a public VPN, or 4G, or any of you lot's connections! I can only think that the issue is with Webex.
I'll advise her to raise a ticket with her mob and let them investigate.
Thanks to everyone for their help!
ZeN Unlimited Fibre 2
Fritz!Box 3390