I've not encountered a no-hints bug. The solver sometimes takes up to 30 seconds to solve the board, though the hint button will appear after 8 seconds if it solves sooner. Are you sure you waited long enough? If it happens again and you're able to save a screenshot (imgur.com will host it for free) it would help me a lot in tracking it down.
I don't want to create a trade between score and hints - I've considered it, but the conversation that happens in your head when you play this game is crucial to its appeal ("oh no I'm dead, oh wait, yes, I'M ALIVE!"). The hints already soften this, but keep the tension ramped up. If you could always buy your way out of failure, you'd never feel the full-force-rush of figuring a way out of what you thought was death. You wouldn't push yourself as hard.
The end-game does need some work though - so there's some more mechanics and adjustments yet to come. I may implement a way to get more hints, but I want you to work for it and feel proud of yourself when you achieve it.