Seems like the device pairs on C-8, but does not stay connected to HE... As it works on C-7 using the same driver, the problem is most probably with the new C-8 Zigbee stack, that is reported by other users and Hubitat engineers are trying to resolve in the last weeks.
You can try also this driver, but I don't think it will make any difference, the problem is not on a driver, but on system level.
