I am having the same problem with being unable to join my friends on PS4 but they can join me whenever I am connected to my Microsoft account on the"Xbox Console Companion" app. Also, I can join them when they are linked to their Microsoft accounts on their PS4 and having their PCs on and connected to the "Xbox Console Companion" app.
I am having the same problem with being unable to join my friends on PS4 but they can join me whenever I am connected to my Microsoft account on the"Xbox Console Companion" app. Also, I can join them when they are linked to their Microsoft accounts on their PS4 and having their PCs on and connected to the "Xbox Console Companion" app.
I hope this helps to fix it.