APPLE INSIDER
The third-generation Apple TV will lose support to the CBS All Access channel in early March, ViacomCBS is telling owners of the model.

On March 4, 2021, the CBS All Access platform will be rebranded as Paramount+. Coinciding with that date, the CBS All Access channel will also stop being supported on third-generation Apple TV hardware, according to a popup spotted by MacRumors.
Source: APPLE INSIDER