That message appears when you are streaming more than the number of concurrent streams allowed by your plan. To stream more than one event at a time, you can add additional streams to your plan in your account settings under "Subscriptions".
If you have enough streams or are not currently streaming another event: When you stop and start the camera, the stopped connection may remain live on the system for a minute or so, and when you try to start a new session, it would detect that you have two live streams running. If you wait a minute and start your new recording session, the issue should be resolved. You may also try fully killing the app and restarting it to force any ghost connection in the background to stop.