I had a similar problem trying to connect to a TVOS simulator with Instruments. When trying to connect with the regular run command (debug) in Xcode was working fine. I realized that the scheme I was using for profiling, had a (Profile) setting that was using Release, instead of Debug. Changing this to Debug, in manage schemes allowed instruments to attach. (This might have something to do with the GET_TASK_ALLOW entitlement, which I don't have set for this project in any target)