Your startup...built a tool to help solve marketing problems for startups and...you're having trouble marketing it to startups? Did I hear you right?
Someone who makes tractors might not be the best farmer. Same for a piano and a musician.
Just because you can make a tool doesn't mean you are the best at using it.
Forget 'being best at using'; has the tool worked for you at all? In this case, the answer is no. So why would I buy it, then?