One year Free Apple TV is not available.
I don't get the apple tv one year free subscription either even though I bought my 2018 mac air after Sep2019.
MacBook Air 13", macOS 10.15
If you followed the description on how to get the offer from https://offers.appletvapp.apple, and it fails, then contact Apple Support for assistance to receive what was promised. Some users have reported getting codes to get the offer that way, when it wasn’t shown when it should be.