The web socket messages from the browser developer tools show the connection starts, but is closed by the gateway after receiving the tab information.
There are no browser engines running on the gateway.
You can check this with the command
sudo docker ps | grep fireglass_engine
Spin up the engines using the following command.
Note: If your deployment is sized differently, specify the intended number of engines instead of the default of 10
fgcli service set-engine-count 10