Can't make apostrophes over letters (like in juan) or make umlauts.

[Wickedgoat]

For some reason, my pc stopped making it possible for me to make "umlaut" or put apostrophes over letters.
I didn't notice untill a few weeks ago. I have no idea why it does it.

 

[Hazinator]

How do you insert those. I always use alt codes to insert mine. Look up alt keys/codes for them. How did you insert them before?