ResMed Res Med S8 Elite Blue Canvas Travel Carry Case & EXTRAS

Description

The bag has been used and is dusty from being in storage. The machine powers on and cycles through the settings fine, but when I press the start button, it runs for a few seconds, stops and says "Check Tube!! Key if done." I don't have any tubes connected to it and don't know how to troubleshoot the machine, so it's up to the buyer to troubleshoot it.
Please look at all of the photos and ask any questions before buying. Thank you!