When I moved the include as instructed, I encountered these errors:
/home/mbl/sketchbook/libraries/FrequencyTimer2/FrequencyTimer2.h:30: error: 'uint8_t' does not name a type
/home/mbl/sketchbook/libraries/FrequencyTimer2/FrequencyTimer2.cpp:27: error: 'uint8_t FrequencyTimer2::enabled' is not a static member of 'class FrequencyTimer2'
/home/mbl/sketchbook/libraries/FrequencyTimer2/FrequencyTimer2.cpp: In static member function 'static void FrequencyTimer2::setPeriod(long unsigned int)':
/home/mbl/sketchbook/libraries/FrequencyTimer2/FrequencyTimer2.cpp:96: error: 'enabled' is not a member of 'FrequencyTimer2'
/home/mbl/sketchbook/libraries/FrequencyTimer2/FrequencyTimer2.cpp: In static member function 'static void FrequencyTimer2::enable()':
/home/mbl/sketchbook/libraries/FrequencyTimer2/FrequencyTimer2.cpp:146: error: 'enabled' is not a member of 'FrequencyTimer2'
/home/mbl/sketchbook/libraries/FrequencyTimer2/FrequencyTimer2.cpp: In static member function 'static void FrequencyTimer2::disable()':
/home/mbl/sketchbook/libraries/FrequencyTimer2/FrequencyTimer2.cpp:156: error: 'enabled' is not a member of 'FrequencyTimer2'
I thought that maybe I should have not removed the include from FrequencyTimer2.h, so I put it back in, but this did not change the situation from the three errors encountered before.