You are receiving this error because you are logged into both platforms simultaneously. Essentially both platforms, Sierra Chart and Optimus Trader, are “fighting” over your single data feed. That is why you were allowed to login initially and some data loaded, however, once Sierra Chart reconnected it cut you off from Optimus Trader.
Rithmic does allow concurrent login sessions, but at the time it appears you were only enabled for one session at a time.
For now feel free to log out of Sierra Chart entirely and close down the platform. Then refresh your Optimus Trader page and you should receive data as you would expect!
In the meantime we will work with your FCM to increase your Rithmic concurrent login status, allowing you to connect to multiple trading platforms at the same time and receive data without any issues.
For any traders who may stumble upon this thread down the line who are receiving this same error message, please email: firstname.lastname@example.org or email@example.com so we can quickly assist you.
Thanks for your patience,
Optimus Futures Support