You said " the download work and now it doesn´t start to download. " What are you downloading? Images? If you are downloading images from a Web page that is over three years old, the Web page might
have changed the links.
This means, the links you store in the TinyDB are possibly no longer valid. Are you using the compiled app you created years ago or are you using your Project code and live developing now?
If you are using the Companion to use the app to download, the links probably are no longer stored in the TinyDB instance; the links only exist and stored on the app you may have installed on your device in 2016. That is how a TinyDB works...the database becomes part of the compiled app. Also, if you are re-compiling your app, make sure you have the latest Companion (2.51a) since your previous Companion will probably not work with the latest App Inventor version (nb 175c).
You must test for this on your app Thomas, The the links are only stored on your Android device in the database.