We have had some reports of YouTube video playback issues on FitnessBlender.com. Thank you for letting us know. We're on it!
We are actively working with YouTube to help isolate the issue, but so far what we know is that it mostly impacts Android mobile users (Android 10 + chrome specifically).
If you are experiencing YouTube videos only showing the spinner / loading / buffering and never playing, can you please fill out this device survey. (it's anonymous).
This will help us coordinate with YouTube support.