If you are still using 6.17.740 and encounter issues, common fixes from Buffer Adjustments

: The app seamlessly renders media up to 4K and 8K resolutions, complete with HDR support and 60 FPS playback.

: Users can still sync their Google accounts to access personalized history and subscriptions across devices. The Future: Transitioning to SmartTube

Re-download the latest available APK file using a side-loading tool like by AFTVnews, which can be found in the Amazon Appstore or Google Play. Exploring Modern Alternatives