Kids messenger app.

i have screen time restrictions on my child ipad for apps. I have some that are allowed all the time. Kids messenger is one app I want to allow my child to use all the time. I can not do this because Kids messenger does not show listed. I understand I can control setting through Facebook. I have setting through the Facebook about as well. My child’s iPad keeps Kids messenger locked all the time. The only way I can unlock it is by daily entering my passcode to give access for that day. How do I set kids messenger app as “always allowed” through screen time on her iPad when the app does not appear listed?