Why doesn’t work PDF file open by PDF.js viewer [with URL]?

I downloaded manually the PDF.js viewer, and it was working perfectly in program XAMPP, but when I uploaded to a web server, it broke down. I uploaded also the web, the build folders and the LICSENSE file several times, but I think the issue isn’t there, however in the URL.

This is the URL’s code, what I’m using:

<td><a class="hrefborder" href="/web/viewer.html?file=%2Fkotta/<?php echo "{$row["elsokotta"]}"; ?>">Open</a></td>

And this is the specific URL. I would open ‘Éneklem A Te Jóságodat – A.pdf’ from the ‘kotta’ folder inside htdocs.

http://example.com/web/viewer.html?file=%2Fkotta/%C3%89neklem%20A%20Te%20J%C3%B3s%C3%A1godat%20-%20A.pdf