Extension validated and signed via the signing API fails to download

Hello everybody!

I’m currently implementing an unlisted, self-hosted beta-channel for Adblock Plus, using the signing API as described in
http://addons-server.readthedocs.io/en/latest/topics/api/signing.html .

The idea is to have an unlisted extension (with it’s own ID) self-hosted for our beta users and keep the main release listed as-is.

I successfully let the addon server sign the extension, checking the status of the current (unlisted) upload returns the following:

"files": [
            "hash": "...", 
            "download_url": "....", 
            "signed": true
    "validation_url": "....", 
    "version": "...", 
    "url": "....", 
    "passed_review": true, 
    "reviewed": true, 
    "automated_signing": true, 
    "processed": true, 
    "active": true, 

However, when i try to actually download the signed .xpi with the given URL in files[], i only get a 404 with

{“detail”:“not found”}

This error, along with every other bits of information saying “success” is not too helpful - hopefully someone can point to where i’m doing something wrong.

Note: There are 4 warnings in “general tests”, which obviously do not prevent the extension from being automatically signed / validated.

Thank you in advance for any help you can provide.
Best Regards,
Tristan Lucas

Is the problem only with the API? Have you verified that the file is on AMO and you can download it from there?