I found how to fix mine after many months... Are you a gamer or have used a program called Easy Anti Cheat? Hit CTRL ALT DEL and look for EAC Easy Anti Cheat and End Task once closed your screen saver and or screen power off timer will work again.. Just remember any games that use EAC will reopen it and leave it running and you'll have to do this every single time... I have sent a letter to EAC about this issue for them to fix it so it will auto close when done with games..
Hope this fixes any issue you have like it did mine..