Joe
Well logic says that it was working before you replaced the cell, and since it is now not working, it should be something that you did...
Since the pump has nothing to do with the salt cell, it has to be something common between the two. A shut off or popped breaker powering your equipment pad, as PoolGate suggests is the first place to start. If you did not shut off the power when you replaced the cell, you could have blown a fuse or circuit breaker in your control center.
Unfortunately, we are not very good Psychics, and it is hard for us to know what equipment you actually have...
If this were my system, I would be looking first at why the pump does not run..
Do you have a single speed pump, 2-speed pump, or a VS pump? What system controls the pump? Timer? Automation?
The more you tell us the more likely that someone here knows the answer.
Thanks,
Jim R.