If your Sennheiser OfficeRunner simply decides it won't turn on in phone mode, but enthusiastically works in computer mode, we may have a quick fix for you!
How to fix it
Ensure BOTH the power cord and USB cord are connected properly. If both cords are plugged in, you can also go to the back of the cube and unplug the USB cord and then check the front of the cube. If the lights have gone out, then there is an interruption in power somewhere. Find where it is plugged in and move to a different outlet, making sure it goes all the way in.
The OfficeRunner will work okay on Computer mode with only the USB cord connected, but the base requires more power to use the Phone mode so the yellow power cord must be connected. This can be confusing, because all the lights will seem normal, but it just won't turn on!