There can be a number of reasons for this.
Rate of pay can often be a prohibitive factor so it is worth considering the industry standard prior to posting a gig.
Try reducing the Tags on your Gig: The more tags you have, the more specific the Gig Helper's profile must be to match your Gig.
Finally, try building up your Own Profile in the App by earning 5-start ratings for Gigs. Perhaps set a Gig at a very accessible time with a good rate to get started. Filling out your simple Gig Owner profile page adequately also lends confidence to Helper's to apply for your Gig.