I got a new PC and blithely installed the latest version of Microchip Studio. The first time I plugged in the Atmel ICE windows set it up and I could select it from the Device Programming menu. When I selected SAMD21G18A as the target, it prompted me to upgrade the ICE firmware from V1.27 to V1.29. I Googled and found https://community.atmel.com/forum/firmware-update-broke-my-atmel-ice and held off. I have uninstalled Microchip Studio and have now installed Atmel Studio 7.0.1931, which has worked well on my other two Win10 PCs. The ICE works fine and is allowed to talk to the SAMD21G18A custom board I have.
Please could someone running Microchip Studio with Atmel ICE firmware V1.29 let me know if you have any issues targeting a SAMD21 using the ICE? It seems slightly strange that no-one else has reported this issue other than Seon, although if we are all happy with the version of AS7.0.XXX we are on, I can understand why perhaps few have has this issue.
EDIT: I previously wrote V1.77 and V1.79 - I meant V1.27 and V1.29, which I have amended above.