ejector pump runs but no water

Last night our ejector pump was running, but didn't pump out any water. As a result, we had flooding from the water softener backwash backing up from the basement drain. Unplugging the pump and plugging in again solved the problem immediately. What happened and what can we do to prevent it? The only thing I can think of is loss of prime. It's nine years old and the only thing draining into it is the water softener backwash via floor drains. Can the salt hurt the seals?

Does it have an impeller still?

Look at the check valve, some times the flapper will break away from its hinge point, and it will move straight up and act like a stopper. Another issue could be something is in the pit that covered the suction hole in the pump. Either way when you unplugged the pump and plugged it back in the flapper, or obstruction fell out of the way and when the pump restarted it did not get in the way this time.

Depending on the pit it could be a small rock...you may want to replace the pump as 9 years old is nearing the end of its usefull life...if it is a Zoeller you could get a new switch for it but I would Just replace it if it was up to me...