Hi,
I also have the issues "Unable to fetch configuration".
We have multiple M64w running as Teleworker appliance. The issue appears randomly.
An exchange device works perfectly fine at the same ISP. Only remove the device from network an add the new one.
In my cases I let the device sit. After a couple of hours the device get its config and starts working fine.
Since now I had 5 devices with this problem.
Whenever I contact Meraki Support and they reply, the problem is solved.