I'm looking for guidance on how to approach management at my present workplace about operational concerns in my department.

I'm looking for guidance on how to approach management at my present workplace about operational concerns in my department. I'm in a new role and staff look to me to find solutions on how to bring up issues to management that concern their team leads and how they manage their specific programs. They don't feel comfortable raising issues for fear of backlash from their supervisors. I have discussed the issues presented to me with my manager, but he follows up with the team leads, who insist everything is "great" when I know it is not. Nothing ever goes anywhere and I am worried we are going to lose good staff because they are frustrated... I am not sure how long I can work under this constant stress :(