Sounds like a connection problem betwen computer and printer. Canon replaced a logic board by the sound of it.
First check you are selecting the right printer (I know it's obvious but as it's been away you may have used an alternative)
Check cable between printer and computer are fully seated at both ends. Good connections?
Try different USB port on computer.
All lights on printer look okay? Power connection good?
Will it scan but not print? Is there a self test function on the printer to check it works okay stand-alone?
In control panel select Printers & Faxes. Select Canon MP500 printer and right-click Select Properties. If you select Print Test page does this work?