I had the exact same error as darrylfromredwoodcity above, nothing in the thread seemed to fix it. Check your system.log, it turned out security software on my macbook pro was blocking the debugserver from attaching to the simulator. It was also blocking dtarbiter from reading DTServiceHub, which prevented my Xcode from running SwiftUI previews. I had to contact my IT team in charge of this security software to get this fixed. This might be worth checking if you have this issue and nothing else works. Here is a very similar issue on an older version of Xcode that was posted on Stack Overflow, where the top answer mentions security software that was blocking processes: https://stackoverflow.com/questions/47942776/xcode-9-2-simulator-debugging-broken-could-not-attach-to-process-id Hope this helps!