I have it at 1440p 144hz then I launch Counter-Strike:GO and alt tab and it goes 1080p and when I switch it to 1440p through the Windows settings I click off the settings window and it reverts the settings I just changed.
Go into your GPU control software (nvidia control panel, or amd catalyst), and make sure it's set to 1440p and 144hz in there, then check your windows display settings and make sure it's set in there, then change it in game.
Go into your GPU control software (nvidia control panel, or amd catalyst), and make sure it's set to 1440p and 144hz in there, then check your windows display settings and make sure it's set in there, then change it in game.