Kevin Feige has said that while the late Stan Lee received a download of the full story of Avengers: Endgame when he was filming his cameo, he unfortunately passed away before he was able to see the finished film.
As reported by CBR, Feige participated in a Reddit AMAA (Ask Me Almost Anything) and a user by the name of abuskeletor asked how much Stan Lee knew of the story of Avengers: Endgame and if he was able to see any version of it before his passing at the age of 95.
Source: IGN.com Kevin Feige Says Stan Lee Didn't Get to See Avengers: Endgame