Len, I would first remove each ink cart and invert 6-8 times gently (don't shake), then simply power up and let the machine go through its self-cleaning routine and see if you get any error messages. If not, print up a nozzle check and try a test print.
If you get a printhead error message, I wouldn't try to force printing as you might draw too much current through the controller board and blow it.
Pete