Praying for forgiveness of a non muslim

Answer

Wa’alayhum as Salam wa rahmallahi wa barakatuhu,

As long as a disbeliever is alive, you may pray for them. You can ask Allah to bless them with guidance, good health, protection etc.

However, once a person passes away as a disbeliever, it is not permissible to pray for his forgiveness.  This is categorically prohibited in the Quran.