AW2518HF, G-Sync compatible?

Hello! I have an Alienware AW2518HF monitor. I read everywhere that it's G-Sync. On the Nvidia control panel I have the G-Sync option on and down says "selected display is not validated as G-Sync compatible." and the problems are this. In cs-go the graphics are very good but when I try to play cod warzone the images goes flickering only in this game. I have to replace the monitor or are some settings for this?

Thanks!