Start a manual regeneration by holding the menu key to unlock the valve, tap the menu key once so Date and time is highlighted, scroll to manual regeneration and hit set, select regen now.
Disconnect the salt line from the salt tank and stick it in a cup of water to see if it draws. If not, then you will need to clean the injectors which you can refer to the link here for pictures and more detail and more things to check to resolve the issue.
https://qualitywatertreatment.com/pages/technical-support
How to clean or replace injectors video: https://www.youtube.com/watch?v=Psd8oPHYOGU&feature=youtu.be
If the drain line is running vertical or a long distance, have them run a shorter line into a bucket and see if the system draws to rule that out as being the issue.