Yes, without paying customers there can be no business. It is great that you have such a userbase! Now you only have to convert a reasonable percentage into paying customers, somehow! If they are not interested in paying for what you have now, then you must identify what they would be willing to pay for. Better is to try figure out, what would they really love to pay for? Which problems do your users have that they would like to pay to get rid of (or substantially reduce)?