Snowflake addon fails connecting to bridge

After the datachannel is opened, the websocket connection to the snowflake bridge fails:

Snowflake: Broker: Successfully replied with answer. snowflake.js:1226:13
Snowflake: Data Channel established... snowflake.js:1226:13
Snowflake: WebRTC DataChannel opened! snowflake.js:1226:13
Snowflake: Connecting to relay... snowflake.js:1226:13
Snowflake: WebRTC --> websocket data: 171 bytes snowflake.js:1226:13
Firefox can’t establish a connection to the server at wss://snowflake.bamsoftware.com/?client_ip=174.138.112.125.
Snowflake: websocket-relay error. snowflake.js:1226:13
Snowflake: websocket-relay closed.

I know the bridge is up because connections through proxy-go instances appear to be working fine.