well a few things to check. since SSB is working, you must have the 4.7k resistor installed, otherwise PTT would not work.
of course check your wiring to the key jack. a short circuit across the interface, when you find it on the board, should get you transmitting on CW.
when this key interface is closed, the raduino should switch the rig into CW - you should see this on the display somehow. note that in the settings (I am not familiar with CEC) there should be a setting that configures either manual key or paddle - see which yours is set for.
also, paddle mode does require some additional resistors to provide different pull-up voltages for dit and dah - this info is on the web somewhere.