Since we have been upgraded to iOS 15 I have been having this issue. I thought that it was because iOS had an update that I needed to do. I have had this issue 3 times now. Two of the previous times I updated my iOS and the app worked again. This is after many times of restarting my wifi router, my Roku, and my iPhone. Then deleting the app and installing it again. Logging out of the Roku app and back in. The only device my app will recognize is our Roku TV which is newer than my Roku Express boxes. I have even tried connecting manually. I have tried everything in the Roku help nothing is working right now and there is no new iOS update waiting to be installed. I have checked to make sure there is no updates to the app itself and the Roku is updated. Super frustrating it was working all day and tonight it’s not.