I have recently joined a group of company where they have MX64 installed between multiple branch offices and as expected unfortunately they do not have any access to these cloud based routers neither the company who had suggested and installed these units are any helpful to share the details. Thought to create a topic here because I also had tried calling meraki support but it is asking for customer support 8 digit number. All I have is a physical unit with me and serial number details.
Due to privacy issues, support cannot give out this info. Resetting the device will not help. It will simply re-fetch it's configuration from the cloud. (It may even never get online again, if there was custom config on the local config page)
I believe the easiest way would be through the installation company.