@kolchinsky thanks for reaching out. Could you PM me the DeviceID? For us to dig in further, we’d like to understand what state and account your device is in.
Normally, you’d need to blinkup the device again for it to be “owned” by a different account. If you only want the device to be “assigned” to a device group under a different account, then you’d need to be a collaborator of that account, un-assign the device from any device group (no need to delete) and switch to the other account to assign the device to a device group.