The FloatingLyrics is not showing synced lyrics
Some music apps such as Amazon Music, Apple Music, and many others do not share information about the current position in the song. Therefore, Musixmatch is not able to show synced lyrics while playing music from those apps.
Here you can find the list of supported music players, and if they support synced lyrics or not:
We're always trying to get more music players to fully support FloatingLyrics, and you too can play your part by asking them to support Musixmatch too!
Please be aware that the Floating Lyrics feature is not available on iOS.