I guess the title says everything, I get prompted for a password when downloading personal data although I do not have such a password because I used Facebook Login.
Have you signed up to Spotify via your Facebook account or you just connected your Facebook account to your Spotify account?
I used Facebook Login thus I do not have a password for Spotify. Otherwise I would not be that surprised by a password prompt.
In addition my archive is only 170 kB, I want something like this: https://bit.ly/2CTE6YG
I’d recommend reaching out to Spotify for more help with this. You can find some more info here on how to do this.
I hope this helps! :)