This happens if there is a transient error on storage side or if backup service is not getting sufficient IOPS from storage account hosting the VM in order to transfer data within timeout period to vault.
Learn more on how to fix snapshot failures due to blocked network access.For Windows VMs, check the VM agent service status in services and whether the agent appears in programs in control panel.Try removing the program from control panel and re-installing the agent as mentioned below.Try moving VM to a different storage account which is not loaded and retry backup. VMSnapshot\agent Version and install vcredist2012_x64. Make sure that registry key value for allowing this service installation is set to correct value i.e.Failed to install the Azure Recovery Services extension on the selected item - The VM agent is a prerequisite for the Azure Recovery Services Extension. value of registry key The DNS name here refers to the cloud service name (usually ending with .cloudapp.net). If you encounter this error, you need to choose a different VM name during restore.