I had just finished doing a workout blender workout which was fine, so I tried
Playing a regular workout in the regular OnDemand and it started fine. I use an
iPad.
It sounds like you're still using the legacy ROKU app. This has now been retired. You need to use the new V2 app that we released about 6 months ago. Here is a link on how to install it: https://cathe.com/cathe-ondemand-roku-channel-instructions/
Let me know if this does or doesn't solve your problem.