Managers are all guilty of going to their office every day and missing problems happening all around them. They assume their subordinates will keep them informed of emerging problems and this is a mistake. Sometimes to find out about growing issues, one must ask and do it frequently.
Try this at least once per day. Go to work and ask each of your employees, “What is the number one problem you have facing you today? Why? For what reason did you feel this was a problem? Explain it and we will see if it can be resolved, sped up, cancelled, altered, split up in parts or manageable bites…etc.”
Try this approach and ask your employees individually so their answers are not tainted by the reactions of others. Ask them privately and note the answers you get. Your employees observe and hear a lot more candid comments than you might in your own role, so do not lead yourself to believe you are aware of everything. You are not.
Ask every day. You may get nothing the first few days, but they will ultimately share their thoughts knowing they have the opportunity given that you speak with them each workday.