Ambify does work with iTunes Match. However, it's important to note that since there is no API that allows 3rd party applications to interact with iTunes Match, Ambify can only access music that has previously been downloaded to the device.
To download playlists or individual songs so that they can be accessed by Ambify, first locate your content in Music.app, then simply tap the download button.
Normally songs which have not yet been downloaded are disabled and displayed using a darker font colour.
However, due to the lack of API, Ambify cannot detect partially downloaded songs and therefore allows them to be played resulting in either a crash or just silent output.
If you are experiencing crashes or silence when playing certain songs please make sure they have already been downloaded onto the device as described above.