I just created a test app which is an app that prints hello world in a text box. But when I add it to testflight, I get a message saying that I cannot download the app. I don't know why and I have installed to the newest mac-version, ios version and restarted my phone and testflight.

Hi, I have made a very simple app (an app that shows "hello world" in a text field). But when I upload it to testflight I cannot download the app on my Iphone. I have the newest version of macOS (15.0.1 macOS Sequoia) and the newest ios version (ios 18.0.1). I have tried to change the name of the app, the change the bundle identifier, tried to change my certificates in the apple developer page, trying to delete testflight, restarting my phone and more. But it doesn't help. I will add that I cannot add external testers to my app in testflight (I also get an issue here). But for some reason I am able add internal testers (but the invitees cannot download the app in testflight) As written above, I just uploaded the most basic app to testflight and I still cannot download it on my phone (I have also tried to invite other testers and still doesn't work on their phone). I have had this issue the last year, and I have tried almost every solution I could find on the apple developer page, the internet and more. It would really help with a solution to this problem. Pls write a solution.