What does the error message “No provisioned iPhone OS device is connected.” mean?

Question

Yesterday I testet a lot on my device. Suddenly I get this error message when I hit Build & Go in Xcode. First, it asks me if it\'s ok to sign with my key. I click yes,

Answer 1

I've had this happen before as well. I'm not sure what caused it either, but in most instances powering the phone off and back on again solved the problem.