document.GetElementByID() Piano Keys

https://www.codecademy.com/paths/web-development/tracks/build-interactive-websites/modules/dom-javascript-events/projects/piano-keys

My code looks the same as in the video walkthrough but I can’t change the content of the element. The alert does not fire.

nextOne.onclick=function(){
nextTwo.hidden=false;
nextOne.hidden=true;
document.GetElementById(‘letter-note-five’).innerHTML= ‘D’;
alert();
}

TO C ![image|690x388](upload://ij7Guy2PkHjt7W6KE2sMfPUrkCa.png)

Is there a good way to debug in Javascript to find out why this line is not working and stops execution of the script?

document.GetElementById(‘letter-note-five’).innerHTML= ‘D’;