There may be lots of people who want to work, just not for what you are offering.  Raise the pay -- are you advertising it, or at least indicating that it's competitive and then some?  And I suppose we have to assume that this is at your location, and involves dealing with the public.  How much of it could be done remotely? 

The biggest challenge for me has always been finding someone who accepts seasonal hours: full time part of the year, part time the rest of the year.  I have been fortunate, although I did lose one long-time employee to cancer and another to a lung transplant.