Hello,
Meraki Dashboard is currently experiencing an issue with newly added devices, devices that has been offline for too long or just moving a device from one network to another are not able to register and be online within Meraki Dashboard. It is being treated with the highest priority and our Dev team is already on it. Please check this post for updates as they will be posted here as they become available.
This is not affecting any devices that are already registered and online within Meraki Dashboard.
Thank you for your patience while we get this resolved.