How To Fix Input Signal Out Of Range Change Settings To 1600x900-60hz

So, I obviously can make the @-symbol by changing the keyboard input to US. But for all time I have had the input set to Swedish and always made the @-symbol with alt 2 . It suddenly stopped working and now I am asking if someone have a solution for making alt 2 working again. Why did it stop working and how do I get it back?