Could you provide more details?
For example, what type of authentication is being used? Are there any alerts on the dashboard?
If you need to resolve this urgently, you can open a support ticket with Meraki via the dashboard, or even call them.
https://documentation.meraki.com/Platform_Management/Troubleshooting_and_Support/Support/Ways_to_Con...
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
Please, if this post was useful, leave your kudos and mark it as solved.