camera connection

Hey everyone, I just joined a new project at my university that aims to use a 3DR Solo (which hasn't flown in three years) for thermal inspections. After spending some time on the forum, I figured out everything I need before it can fly again (new batteries, Open Solo, etc.), and now it's time...

I had the Solo app connected but when I pressed Fly Solo on the app to view the camera it opened the camera for a second and then it closed. This kept happening. I tried opening and closing the app, rebooting the phone and rebooting Solo and the controller. Still no go. I checked the HDMI cable...