How ancient is this controller? If its really stubborn, after the machine has homed, try keying in G92 X0Y0 in MDI and then execute it. Then try setting a work offset. Or if you prefer, you can dispense with setting the work offset, simply move your machine to the work datum, and execute G92 X0Y0 at that location. If you do this in MDI, then the machine position will be established for as long as the power is on, and you don't need to write the G92 into the main program, which has certain dangerous ramifications if you restart out of position.
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)