Is there anyone who has the same symptom?

I'm a PC user and I bought this game to play co-op with my friend.

But if I open the Uplay app in the game to invite him the game stops right after I close it so I never can invite him.

There is no problem if I open steam app and my friend also has the same symptom exactly like mine.

Is there anyway to invite friends without using uplay app or how can I fix this problem?