Is it possible to play Playstation 4 and 5 consoles at the same time

I am struggling to get proper support from PlayStation where I have two consoles PS4 and PS5. My sons are trying to play different games at the same time on their own accounts. One of the accounts has a PS plus subscription which are registered on both consoles.

I have PS4 as primary. Many months ago, I was able to have both of the consoles playing games at same time, it is no longer working.

Any advice to resolve this?