I installed the latest JFlash (6.12d) from Segger's site, and it updated the JLink firmware.
However when I try to program the hex files downloaded from www.nordicsemi.com/.../Getting-started-with-the-nRF52840-Preview-Development-Kit
I get a message in JFlash
"Sorry, no valid license for J-Flash found" "J-Link S/N is 683404738"
Edit. I can read back using JLink, and I did select the correct device, I just can't program due to this license issue. I can program by copying hex files to the mass storage drive "JLink", but it would be better if JLink was working (fixed)