I have AppleOne and have my appletv app on my smart tv…Does it only play on my iPad?

Apple TV+ content should play on any of your devices with the Apple TV app, when signed in with the Apple ID account that has the subscription. The other parts of the Apple One bundle do not apply to third party devices, such as Vizio TVs or Fire TV devices.

Verify that you are (still) signed in to the Apple TV app.

Apple TV Plus is tied to your ID, so as long as you are signed in with that same ID you can access the subscription via the app on the Vizio. If it isn't working then try logging in again, and if persists you may need to contact Apple.