[ig1]

I imagine they rejected you because you're a sole founder, plenty of companies who apply to YC and don't get in do well. YC don't have a magic ball that tells them who'll succeed and who'll not.

[jivejones]

That is a possibility, I probably need a co-founder / more team members.

[ig1]

Very very few single founders get accepted into YC, those that do tend to have strong track-records and significant market traction