Unable to join my friend's world

My friend plays on PS4 and he has 1.16.61 which is only for PS4 while I have 1.16.40.
I am unable to join his world because we are on different versions.
I can't join his world, but he can join mines.
I've only been able to join once, but that time only.
I was randomly able to join, and I'm not sure why and can't replicate it.