The only local persistent storage on TVOS is NSUserDefaults.
Does PlayerPrefs wrap NSUserDefaults on TVOS? If not, what is the standard method of persistent storage via Unity for this platform?
From what I see there is no “Persistent” storage on TVOS, Applicaton.persistentDataPath is a no-go.
As a quick patch, what you might want to use is custom TVOS native plugin that will return path to Temp or Caches directory, that worked for me, but that data will be removed once HDD is full…
So basically start working on cloud save system, and force users to sync often 
Best of luck