It seems that you are running the Steam version of PowerBeatsVR, but the game could not start because of a problem with SteamVR. SteamVR is required and must be running for all VR games running on Steam.
Please first ensure that SteamVR is installed; it can be installed directly from the Steam Store (it’s free).
If SteamVR is already installed (you should see a VR icon in the upper right corner within Steam), please make sure it is running and is properly set up (it should display your headset and controllers in green). In case SteamVR hasn’t initialized properly, it can help to close it together with any software related to your headset and start them again.
Afterward, start PowerBeatsVR and enjoy your workout.