Go to: Network-wide > Monitor > Event log
Filter the log:
Select "Security Appliance" from the dropdown.
Deselect all event categories except VPN.
Search for:
VPN client connected
VPN client disconnected
For more details, please check the documentation.
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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