Pitch Wars is tough, and I say this as someone that tried twice to get picked as mentee, got requests, but never got selected.
The GOOD news, however, is that Pitch Wars is just one venue, and not the only one, by far. My novel that's coming out next year is a Pitch Wars 2017 rejectee, so even if the mentors at Pitch Wars don't like your book, that DOES NOT mean an agent won't like it, and an editor might not eventually like it too. Just remember that sometimes books get rejected not because they're no good, but because they're "close enough" that sometimes the mentors don't feel like they can be much help. Other times they reject it because they feel there's something there, but the timeline for getting it ready might not line up with Pitch Wars scheduling for submission to agents.
So keep at it. It does suck when you get requests and don't get picked, believe me, I've been there. But it's far from your only shot.