In combination with iTunes Store movies (or music or books), “Authorize” is used for computer playback (Mac or PC), not the Apple TV box per se (unless Home Sharing or AirPlay, but that isn’t needed, as the Apple TV box can play this content without using Home Sharing or AirPlay).
Authorize or deauthorize your computer for iTunes Store purchases - Apple Support
Authorizing links the device uniquely to an Apple ID account. Users should de-authorize computers that are no longer in use by you, as there is a limit of 5 computers per account. You can try de-authorizing all your devices, then re-authorize devices when needed, to make sure it is not about a forgotten device or the limit.
Aside from unintentional setting resets, updating macOS wouldn’t affect this. Most users have been playing iTunes Store content with every version macOS without this error. The version macOS itself is not the cause.
Try playback on the computer without Apple TV box involved. Is that any different?