Why doesn't my team tell me about problems until it's too late?

You say your team doesn't bring you problems. Look at yourself first, not them. Somewhere, you taught them this. Maybe you reacted badly to bad news once and never noticed. Maybe you rewarded only good news with your attention and warmth. This is not a flaw in them. It is a report on you. A team learns the real rules of its leader within weeks, not years. They are not slow learners here. They have learned perfectly. The silence is the lesson, handed back to you. You cannot fix this by telling people to 'speak up.' That is just words, and words are cheap. Fix it by changing what happens the next time someone tells you something true and uncomfortable. That is the only proof they will believe.