I checked other topics and couldn’t find this type of problem. Although my code works, error tab tells me it is not working.
No audio plays when the Q key is pressed : expected true to be false
But it plays when Q key is pressed.
Here is my code https://bitbucket.org/ilknurultanir/drum-machine/src/master/
You can check it from https://serene-stream-13297.herokuapp.com/
Warning: Invalid DOM property `class`. Did you mean `className`? in div (at Drums.js:67) in div (created by Container) in Container (at Drums.js:27) in Drums (at App.js:9) in div (at App.js:8) in App (at src/index.js:8
This error lists several files because you used bundled them.
You’d be surprised how errors such as these snowball in these kind of scripted apps especially with artificial checks like the FCC tester.
It wasn’t the issue but you’re right. Thanks for the help. 
Solved
The issue was after i clicked a button and then pressed a keyboard buttonit wasn’t working. Because it was focused on the first key i clicked. If you dont use <a> but <button> it would be good to check it out. Hope it helps.