Given that the unit had been allowed to run out of salt you can expect that the water contained within your system i.e. hot water tank etc would remain hard until the new refill of salt was made. Water softeners only use the salt brine solution when they are “backwashing” that is cleaning the scale and lime from the resin stored in the tall cylinderical tank. It could be that all the unit needs is for you to press or turn the button on the head piece that starts the regeneration programme working again. You will know when you have the right button or switch activated after about 5 minutes the unit will start washing itself out and sending the “dirty” water to the waste pipe. It usually takes depending on the model approximately 90 minutes for the whole backwashing process to be completed and softened water to start flowing. Check that if the unit has a power driven top head that the power is in fact being supplied to it. Let me know how you get on.
Selgas Services Ltd Craftsman Gasfitters, Plumbers, Electrical Service Technicians