Yes, there is a difference in the labels displayed for offline status on the MX, depending on the cause of the issue.
If the MX loses connectivity to the Meraki cloud, it will display a status indicating "no connectivity". This typically means that the device is still powered on, but is unable to communicate with the Meraki cloud.
If the MX experiences a power outage or is rebooting, it will display a status indicating "rebooting/no power" or something similar.
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
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