I have been having the same issues described in this thread. Only external interrupts 0 and 1 seem to work. Unfortunately these are associated with pins 2 and 3, and I need those for i2c.
Does anyone know of a reliable fix for the IDE to support the No. 2, 3 and 4 interrupts on Leonardo (nearest thing to Pro Micro) as described here?
I want to minimise power consumption in a battery powered circuit by putting the Micro Pro into a low power sleep mode, and waking it only on events from 2 pushbuttons and the 1Hz square-wave output from an RTC.
My current solution uses the Sleep_n0m1library, sleeping for 50ms periods and polling the inputs between sleeps.