Could not find Cortex-M device in the JTAG chain. Tiva C LaunchPad

Question has been asked before but many years ago without any resolution that I could see. I have a TIVA Launchpad and I get the error Could not find Cortex-M device in the JTAG chain. Tiva C LaunchPad. My device has been programmed before and still has the usual beginner flash LEDs program on it. I've checked switch to Debug. Still no joy. Any ideas ?