I have an 930c. The manual says that cure for ALL the lights flashing may be a reset.
1,Turn off the printer using the power button and turn it on again.
2 If this does not work turn of the power using the power button
3 unplug the printer.
4 plug the printer back in
5 Use the power button to turn it back on.
Hope thats some help Not sure how close the 930 and 940 are.
I assume you have checked if the arrow on the print cartridge cradle lines up with one of the cartridge status icons when you open the printers top cover while the light continues to flash.This indicates the problem site.
The light stops flashing when you open the cover if it is a low ink problem.