I am having the same problem, I can't get the Keylab 49 to leave Update mode no matter how I turn it on/off or how long I wait. If I power it up using just the power switch (or plugging in the USB cable with the power switch on), the LCD says "Update" and the Sound, Multi, and Edit lights are illuminated. If I turn on the power switch with the Octave Down and Octave Up buttons held, I get the exact same result. If I turn on the unit with the Sound, Multi, and Edit switches held, the LCD says "AnalogExperience KeyLab" for just a second or two and several of the lights on the unit flash 2-3 times. Then, the LCD display changes to "Update", and the Sound, Multi, and Edit lights turn off.
I contacted Arturia support a few days ago, so I still expect to maybe hear something, but I wanted to lend my voice to this thread as well.