If you don't add salt in your brine tank & not maintain the salt requirement then you will not get soft water. You will get hard water instead.  In this case, replenish the salt level in your brine tank as soon as possible. Please note that you'll not get immediate effects. You'll get soft water supply back within 2-3 days in the entire home. Always keep your brine tank half-filled with salt to avoid the above-mentioned situation. Check the level of brine tank every 2-3 days.