I tested it with the 3 exemples available for Control Chain (Button, Exp to CC, Pot).
The arduino code is well compiled and uploaded to the Arduino Uno with no error.
(My Mod Footswitch works fine and is well detected by the Mod Duo.)
Tested with different cables, I don’t have any notification on the Duo, only for the Mod Footswitch.
I installed correctly TimerOne and ControlChain v0.5.1 libraries.