Hello Jon Gibbs
Welcome to Microsoft Q&A Platform, thanks for posting your query here.
Based on the information you provided, it seems that your virtual machine is currently unavailable and the Azure monitoring system has received information regarding the unavailability of your VM. This event is tagged as "Unplanned" and represents an automatic failover.
Automatic failover can be caused by software bugs or infrastructure faults like compute, network, or storage failures, or power outages that affect the availability of the Azure Resource.
Other reasons could be due to unplanned maintenance, host server reboot, or connectivity loss to the remote disk.
To get more information about the root cause of the issue, you can check the Resource Health section in the Azure portal.
If Azure has further information about the root cause of a platform-initiated unavailability, that information may be posted in resource health up to 72 hours after the initial unavailability.
If you are still experiencing issues after checking the Resource Health section, and your resource remains in this state for an extended period of time, please open a support case so that support team will be able to assist you further on this.
Hope this helps.