Hello @Al, by the description of your issue it appears that your cellular provider may require a custom APN for the Meraki device to be able to register the dongle. - Please refer to the bottom of the following Meraki support article - https://documentation.meraki.com/MX-Z/Cellular/3G_-_4G_Cellular_Failover. My recommendation would be to reach out to your cellular provider to find out the 'APN' required and then opening a support case with Meraki support to pin the APN to your Z1 device. If this doesn't fix your issue I'm sure Meraki support will be able to assist you with troubleshooting the connectivity issues from there on-wards.
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