If the button doesn't work, the average user is going to say "this most be broken" and then use a competitor (or contact your support). That's why it's really important to error-proof one's design (eg https://en.wikipedia.org/wiki/Poka-yoke).
So instead of the button failing because you didn't check a box, pop up with a message telling them "Please click $box before continuing". Or if you want to be fancy, feed them whatever form you're giving them piecemeal, so that they can't continue until they finish this small part (e.g., have them input a name, then the next page only has a spot for an address, then the next page only has a spot for card information, then the next only has a spot to select shipping). Simple bite sized chunks anyone (well, anyone you would ethically want to sell to) can understand.