In VC it's "team, market, product".
In most cases people are happy to give you their reason why they think it's not such a great investment.
You might want to go back to people's reasons for rejection and make sure you took away the right lessons learned.
If there's some underlying oddball reason they're unable to articulate clearly, like you didn't pass due diligence because they have you confused with a mass murderer of the same name, or the reasons are otherwise it might help to work with an intermediary who is familiar with the VC process. Either your experience should put you in touch with possible mentors/board of advisors, or as a last resort you could give someone with a record of success a stake contingent on getting you over whatever hurdle is blocking you.