Thanks for the feedback! What OS and browsers are you using, please? Did you receive any error messages?

It worked fine for me with correct messages, including across networks (I tested from my mobile phone network to my home network, not only just on the same wifi connection or same computer).

It should work in Chrome, Firefox, and Safari across any device and operating system. Normally you don't need to open any firewall ports either. It uses WebRTC: https://en.wikipedia.org/wiki/WebRTC