Firebase Web / Uploading file to Firebase Storage Not Working

I've watched 'Getting Started with Firebase Storage on the Web' on YouTube. I applied it to my code, and it worked perfectly. But I wanted uploading step separately from selecting file step. So I created button and added event listener to the button. (Thus, I basecally separated the code from the video into two event listener functions because, again, I wanted selecting a file and uploading the file two separate actions).

I just don't understand why it's not working. It doesn't give me any error on my console log. Could anybody please tell me WHY this is not working and HOW I can fix this? Thank you.

My Two JavaScript Functions