Audio files don't play in pool

Hi there, I’m new to Cubase and hope to get some help here.

When using the “pool” I’m not able to play the audio files, neither before nor after import like done in these tutorials:
play before import (in search): https://youtu.be/sRd9jSNJCss?t=2m45s
play after import: https://youtu.be/sRd9jSNJCss?t=1m36s

When I do the same, the play button just stays pressed down and nothing else happens. This happens for all files i tried so far (different file formats and lengths). When playing the files in any other audio player they work just fine.

Any ideas on this?