Bad Gateway (502) errors are usually caused by network issues or by an invalid response from one of the servers along the transmission route.
This issue is typically intermittent and network-related rather than Vivox-related. If you continually see this error, check the network configuration of the device or the local network configuration (for example, proxy or firewall restrictions).
The cause of this error is beyond the control of the developer. The best recourse is to implement retry logic to wait for a certain amount of time and then try again. Configure this retry logic to give up or wave off after a few failures. This error is often seen during the connector create or sign in process, but could also occur during other actions.