Monitor turns black when playing LOL on the rog ally

[Helfyro]

Hello, I have a problem on my rog ally and can't find a solution about it. I recently bought a monitor to play LOL on the rog connected by HDMI. It connects normally while duplicating the screen, I can use the launcher but when the game starts, my monitor is turning black and there's just the rog ally screen even if I'm still duplicating the screen. I have this problem only with LOL, other games on steam don't have this issue. Do someone knows how I can solve it ? Thanks.

[Aureliannn_ROG]

Hi @Helfyro ,

based on your question, may I inquire when the issue started occurring? 
Have you tried connecting the monitor to other devices to see if the black screen issue persists? 
What is the model of the monitor you are currently using? 
Are you using HDMI to connect the Ally to the monitor? 
If you try using different cables, does the problem still occur? 
Does the issue only occur with League of Legends (LOL)? 
Have you ensured that all drivers/firmware are up to date? 
Would you be able to record a video demonstrating the issue of the Ally causing the monitor to black out when opening LOL? 
Your assistance in providing this information would be appreciated. 

Thank you.