mastermax2 :
no one help me ?
Hm... I think you might have been running DSR. To re-enable the option of 4k, do the following:
-go to NVIDIA control panel
-click 3d options
-go to DSR factors
-Turn 4.00x on
Please note that this is NOT actually 4k, but an option that renders your game in 4x the original resolution then downsamples it to your original resolution, improving anti aliasing quality.
Besides that, you should check your monitor settings if the resolution isn't set to 1080p whereas you would be able to turn on 4k.