Hitting the same thing. Newly wiped machine, installed fresh macOS 11.1 & Xcode 12.3, enabled developer mode from the command line as per one of the responses here. App for macOS builds fine but debug fails with: Could not attach to pid : “3034” Domain: IDEDebugSessionErrorDomain Code: 3 Failure Reason: attach failed (Not allowed to attach to process.  Look in the console messages (Console.app), near the debugserver entries when the attached failed.  The subsystem that denied the attach permission will likely have logged an informative message about why it was denied.) User Info: {     DVTRadarComponentKey = 855031;     RawLLDBErrorMessage = "attach failed (Not allowed to attach to process.  Look in the console messages (Console.app), near the debugserver entries when the attached failed.  The subsystem that denied the attach permission will likely have logged an informative message about why it was denied.)"; } In the system log I'm seeing some logging around DTServiceHub but there are no clearly-related error messages in the log.