In variant.cpp file, replace the line
- { PORTA, 17, PIO_PWM, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM), No_ADC_Channel, PWM2_CH1, NOT_ON_TIMER, EXTERNAL_INT_1 }, // TCC2/WO[1]
with
+ { PORTA, 17, PIO_PWM, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM|PIN_ATTR_TIMER), No_ADC_Channel, PWM2_CH1, TCC2_CH1, EXTERNAL_INT_1 }, // TCC2/WO[1]
The variant file is in Arduino15/packages/arduino/hardware/samd/1.6.x/variants/arduino_zero. Arduino15 directory is in User\AppData\Local\ (windows), and User/Library on Mac.