From your post, I can't tell if you debugged it on a real 877. The 877A and 877 code should be identical. If it worked of a real 877, is should also work on the 877A but a simulator isn't good enough. There are many things that will prevent it from working.
Things to look at:
- read the program back to make sure it actually got programmed
- verify your hardware (+5V, gnd connections, mclr pulled to +5, crystal/caps or resonator)
- if you have an o'scope, check the oscillator pins (osc1 or osc2) with a high impedence probe.
- write a super simple program that toggles 1 pin on and off every second or so and check the output with a dvm or led.