The E1 error on the WaterBoss water softener means "Home not found." If you are seeing this error, it means your controller is likely not properly connected to the water softener. According to the WaterBoss instruction manual, the best way to solve this problem is to unplug the unit to reset it, and then check the controller connections. If that doesn't make the E1 error go away, there may be a more serious problem with your water softener.
Trace the WaterBoss water softener's power cord to the electrical socket.
Grasp the base of the wall plug firmly and pull it away from the outlet to unplug it.
Inspect the plug connecting the water softener to the handheld controller. Push it in firmly to ensure it's properly connected.
Plug the power cord back into the wall outlet. That resets the system. The "E1" error should be off.
If the "E1" error does not clear, repeat the process. If that doesn't work, contact your WaterBoss vendor for service.