Many companies nowadays protect against outside attackers by shielding computers or their networks with Firewalls and only allowing certain traffic.
You might experience that Butter will therefore not be accessible to you as a host or to the guests you've invited to your session. If your facilitating sessions where your guests might face these firewall issues, we recommend running a trial session with one of the future guests before you schedule and plan the entire workshop.
If you work at a company where you want to get Butter whitelisted, you can share this guide containing instructions for your IT department:
The best option is to not have any VPN and firewalls that block the usage of Butter, but for good reasons, this might not be possible.
If you're on corporate WiFi, you might be inside the corporate VPN and firewall. It would be good to add this list of domains to their "allow list":
The first four make up our core infrastructure. Twilio and Xirsys domains are TURN relay providers that we use to route audio and video for users behind firewalls.
Firewalls can also be configured to allow UDP hole punching to the following ports: 40000 - 65534 for audio and video. Usually, we don't need this, and #2 should work well.