A late-summer country music festival in Panama City Beach, Fla., has been scrapped, and local officials are just as confused as fans. Kickoff Jam was canceled with a message that hardly explains what happened. Carrie Underwood, Garth Brooks and Alabama were set to headline the three-day Kickoff Jam from Aug. 30 to Sept. 1.TuneIn.com — where Brooks programs a slate of stations including the Big 615 — was the official media partner for the event.Kickoff Jam was presented by producers of Gulf Coast Jam, a popular three-day festival in PCB in early June.Why Was Kickoff Jam Canceled?Officially, Kic…