Assassin's creed 4: Black flag not opening after the first time

For the first time after installing the game runs fine but when i want to open the game for the second time I only get a moment of black screen and then i go back to the uplay launcher. The worst thing is that the game is running becouse the play button in uplay is greyed out. This only happens on my sisters setup whith
AMD Radeon 5 2nd gen
RX 570
16GB Ram
On my setup with
Intel i5 6gen
GTX 960
16GB Ram
everything runs well. Both systems are running popOS but the intel one has KDE Desktop enviroment