Chrome Download Attribute not working

Reading the comments, I had the same issue as @buffer-overflow and found this in the issue:

I'm guessing that the web page and the download are on different origins. We no longer honor the download attribute suggested filename for cross origin requests. Clicking on the link still initiates a download. But the the filename is only derived from factors solely dependent on the server (e.g. Content-Disposition header in the response and the URL).

So no chance I could make it work ... :(

After some research I have finally found your problem.

<a> download attribute:

If the HTTP header Content-Disposition: is present and gives a different filename than this attribute, the HTTP header has priority over this attribute.

If this attribute is present and Content-Disposition: is set to inline, Firefox gives priority to Content-Disposition, like for the filename case, while Chrome gives priority to the download attribute.

Source

HTTP-Header Content-Disposition