Umlaut
I can't type umlaut using my US keyboard anymore. I can't exactly say since when but it's been a few day.
so I used this option for umlaut to type German words, to hold down the 'a' key (for example) then some forms of 'a' letter such as a umlaut appeared above and I clicked it.
but now nothing happens as I hold the key.
what should I do?
MacBook Air 13", macOS 10.13