Hello MarissaCornell,
Updating and restarting your Apple TV were both excellent troubleshooting steps.
You can isolate that further by deleting and then reinstalling the app using the steps below:
1. Select the app you want to delete, then press and hold the clickpad center (Siri Remote 2nd generation or later) or touch surface (Siri Remote 1st generation).
2. Select Delete App, then select Delete or Offload.
Offloading an app removes it from the Home Screen to free up storage, but retains its data in case you install it again.
Deleting an app also deletes its data. You can download any app again that you’ve purchased on the App Store, free of charge, but the data may not be restored.
You can also find those steps in this resource: Customize the Apple TV Home Screen - Apple Support
Should you continue to experience difficulties with just that app, you'll want to reach out to the developer: How to contact an app developer - Apple Support They'll be in the best position to troubleshoot their particular app further.
Take care.