I just got one to start. I changed the device the tests were set to run on, from an iPhone 12 to iPhone 13 Pro Max, and then it started.

I am also having this problem. In Xcode 15, in every UITest failure, I can select the failure, and it goes to the "Automation Explorer" where I can replay the test at every step and see the screenshots to the right. In Xcode 16, the view on the right that shows the screenshots is simply gone, with no way to bring it back. That view was incredibly helpful, and I have no idea why it's gone or how to restore it. If I switch back to Xcode 15, it's there and working fine.