You've set TRIS for PORTD.7 for Output?

You've checked that anything else that share that pin is switched off (eg any Analogue or other devices).

You've connected your LED the correct way around (with a current limiting Resistor) and it works?

Personally I like to use HIGH and LOW... eg...

HIGH PortD.7

eg

If AlarmH1=AlarmHour then
HIGH PortD.7
else
LOW PortD.7
endif