You should hear a song in Chinese ~ Make sure you have the media volume on and up :: Settings > Sound > Media volume. The call volume doesn’t effect the test song playback.
The speaker module may be loose, you could check that. When did you buy the FP3?
If their is a fairphoneangel near you you could swap speaker modules maybe.
Otherwise be sure to put in an official support request, FP may send you a new speaker if you want to try that, but an official request for support is essential to use the warranty
One thing you will be asked by support is to do a factory reset so you should do that maybe before you ask officially.