UNPLUG FRIDGE FOR 30 SECONDS. Out of the many repetitive answers above, I only found this once - by Bob Wasson.
Bob! You Da Man! I tried a lot of things - that didn't work. I KNEW it had to be something simple as the cause (me improperly turning out the Replace Filter light [I followed the filter manufacturer's instructions instead of those in the manual]) the cause was simple. And P.S. To The World - The unplugging thing also worked for my printer. Thanks, Bob. And you're welcome, world.