Remember that you need to set the right settings in terms of Region and Availbility zone, etc. It was also my exprience that you need to do things in a certain order, as the vMX App in Azure will "lock" things.
From what I understand, the vMX token from the dashboard is typically used to associate the vMX instance in Azure with your organization on the dashboard. The "lifetime" usually indicates the time window during which the token can be used for this association, starting from the moment it's generated.
If the vMX is not online in the dashboard, even though you've confirmed that the instance is reachable from Azure hosts, it suggests there may be a problem that's preventing the vMX from communicating with the dashboard. This could be due to network routing or firewall issues, for example.
The token's "lifetime" usually does not affect the vMX's ability to stay online once it has been successfully associated with your dashboard organization. Therefore, if your vMX was never online in the first place, re-generating the token and trying again might be worth a shot. But, it's also important to investigate potential network or firewall issues that could be blocking the vMX's communication with the dashboard.
Here are a few things to check:
Make sure the vMX has the correct network settings and security group permissions in Azure to allow it to communicate with the dashboard.
Check if there's a firewall in your network that's blocking the necessary ports. The vMX needs to be able to make outbound connections to the Meraki cloud on certain ports.
Review the vMX deployment guide and ensure that all steps have been followed correctly. This includes setting up the virtual network in Azure, configuring the vMX instance, and so on.
If you suspect that the token might have expired before the vMX was able to connect to the dashboard, you could try generating a new token and entering it in the vMX settings in Azure.