Are you using the L2TP connection or Anyconnect?
Is your MX's WAN configured with a public IP or is it behind a NAT (Private IP)?
If it is an L2TP connection and the WAN is configured with a private IP (NAT) or even CGNAT, the Client VPN will not work.
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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