issue with using external device for playback

I am trying to use my Logitech Z305 laptop speaker to play back Audacity (2.2.2) recordings made on my Macbook (OS X 10.11.6) The Logitech is selected/checked on Mac System Preferences, but on Audacity the playback device drop-down menu will only display Built-in Output. The Logitch is working fine with other apps, YouTube etc. Any suggestions?

(NB I’ve already asked Apple for help and after trying unsuccessfully to fix the problem they suggested I contact Audacity as the problem only seems to exist in relation to this app).

issue now resolved by clicking on Transport/Rescan Audio Devices.