I made sure all the files kept their original names and that before I started using the decks on my android I made sure to “download missing media” and it worked by some miricle. I’m not sure what did it but it works and I have installed three decks with sound!!!

Hello all,
i had the same issue.
Even if you did everything right (setting up dropbox and so on), it might not download the media files.
My solution was No.1:
In order to trigger media download:
1) The best way is to answer at least one card from the deck and then use “Sync All”. This causes a proper media download as expected with all the correct dialog boxes.
OR
2) Alternatively, click on the deck then Sync that deck individually. It feels like AnkiDroid then crashes, as it displays some blank screens, but it’s only a temporary hang until the media finishes downloading. I think there is then a brief popup screen saying that media was downloaded, but there are definitely some missing UI elements here that should indicate what is happening.
OR
3) Apparently, as in issue 612 above, manually creating the deck’s .media directory before downloading the deck will cause media to be correctly downloaded on the first try.

I found the stuff above here:
https://code.google.com/p/ankidroid/issues/detail?id=405

Thank you everyone for this thread, because this lead me to the other thread and solved my problem.
I hope someone with the same problem will find this. :D

Best regards, Lars