Because your device likely isn't certified, the Play Store app might be missing or crashing. Here is the legacy method to get it running:
True Android TV OS (the leanback interface with rows of cards) was introduced with Android 5.0 (Lollipop). If your device says "Android TV 4.4.4," it is technically a tablet/phone version of Android hacked to run on a TV. You do not have the official leanback launcher. Consequently, the Google Play Store on these devices is the mobile version, not the TV-optimized version. google play store for android tv 4.4.4
Analysis of Google Play Store Compatibility and Alternatives for Android TV 4.4.4 (KitKat) Because your device likely isn't certified, the Play
Some advanced users have had success by uninstalling Play Services updates (Settings → Apps → Google Play Services → Uninstall updates). Then clearing cache/data on Play Store and rebooting. This sometimes lets the Play Store fetch older compatible apps again — but it’s a temporary hack. Analysis of Google Play Store Compatibility and Alternatives