Getting the same issue trying to build a project in Github Actions on macOS 13 and Xcode 15.

I solved the problem by deleting the "copy files" phase that I had in my helper app, and instead putting it in my main app. Now the app builds and archives perfectly!

App sandbox doesn't seem to cause any issues, as I had it enabled before and even after removing it nothing changed, however you mentioned something about "Code sign on copy" being set which may be the cause of my problem, as it's not set to anything and I don't know what to set it to (this would also make sense because in the error it says that the helper app isn't codesigned, when in my settings it should be) Whenever I try to set "code sign on copy" to anything, it doesn't change as if rejecting my input, so I don't know what to do here.

Both of the apps are in the same project with automatic signing.

so I've fixed the issue by putting all of the code that loads the username and password into the function that runs when the internet is connected, so the final code looks something like this: monitor.pathUpdateHandler = { path in if path.status == .satisfied { let usernamestored = defaults!.string(forKey: "username")! ... let task = URLSession.shared.dataTask(with: request) { (data, response, error) in {...} task.resume() } }