Hello robashep,
We would not advise to change your Apple ID password if you're able to log in successfully with your Apple ID elsewhere.
We did find this information about the Apple TV 3rd generation set up, to make sure you're trying to log in to the right place.
Set up your Apple TV (3rd generation) - Apple Support
Change settings and check for updates
• Go to Settings on your Apple TV to hide apps from the Home screen, change AirPlay settings, and check for new software updates.
• To buy or rent movies from the iTunes Store or Apple TV app, go to Settings > iTunes Store and sign in with your Apple ID.
• You can also sign in to iCloud to see your iCloud Photos and use Family Sharing on your Apple TV. Just go to Settings > iCloud and sign in with your Apple ID.
• If you have two-factor authentication set up for your Apple ID and are asked to enter a verification code, learn what to do.
For additional assistance, we'd advise to contact Apple Support for the Apple TV.
Get Support
Under "Tell us what’s happening", type in Apple TV 3rd generation, to get started.
Take care!