Your business model is a common one that is generally referred to as a marketplace application. So common is this type of app that your website is literally lost in an ocean of millions of similar apps.
I think that you may have over-estimated the value that you have offered to your potential users, or at the very least failed to express it in a compelling fashion.
For example, you complain that you have traffic, but not many vendors. Why are people visiting your marketplace if there are no vendors? There has got to be a problem with that traffic because why in the world would they visit a marketplace app without vendors?
It’s A Chicken Or an Egg Dilemma
Why would shoppers visit and browse your marketplace without vendors?
Why would vendors list products without lots of shoppers?
I know you said it is free to use your app, but still, it has no value until you get real commerce going on there. Yes, you may have traffic, but likely very low-value traffic if they are coming to a marketplace app with few or no vendors. No vendor wants that kind of traffic. This is always the biggest challenge for a marketplace app.
Most new marketplace businesses require a lot of promotional investment just to get it started. Here are a couple of ideas for getting it off the ground:
Consider creating a major launch event that will be heavily advertised and promoted. Set it well enough into the future that you can get vendors signed up in anticipation of the launch event. That may create some excitement and anticipation, and vendors love to get them some free advertising.
Do away with the completely free model and instead set a price that reflects the value you want to target. You can then offer to waive the first year’s fees to the charter vendors, set a limit like “first 50 vendors are free”, all new vendors will have a signup fee, or transaction fee, after those first 50.
Advertise for vendors, then advertise for shoppers, then advertise for more vendors then advertise for more shoppers. Rinse and repeat, over and over. Start small and scale up with each new cycle. That has worked for other marketplace apps. It’s a grind to get started, the payoff comes later after all the hard work is done building your user base.