Win32 error: The network path was not found. Code 53

This error means that the Veeam Backup & Replication server cannot connect to the Windows guest’s OS feature to deploy guest processing components. This path will be the ADMIN$ share (\\hostname\admin$) of the guest itself.
 
These components are deployed directly from the Veeam Backup & Replication server. If networking is inherently impossible to the guest from the B&R server (different networks, firewall, etc), processing protocol may require inversion (VMware only).

When this error occurs, there are a few items to go through:
 

• Make sure the Windows time on the Veeam Backup server is the same as in the guest OS.
• Make sure you do not have a firewall in the way (you can try disabling it for testing).
• Make sure you can connect to the admin share (for example, \\Server Name\admin$) with the same credentials as provided to Veeam Backup & Replication for VSS.
• Make sure the VSS writers are set to automatic in the guest OS.
• Make sure you provide Local Administrator (MACHINE\Administrator) or Domain Administrator (DOMAIN\Administrator) account privileges.
• Make sure the guest OS is in the same network as the Veeam Backup server.
• Make sure File and Printer Sharing is enabled in the guest OS.
  • ​Once File and Printer Sharing is Enabled on the guest OS, ensure to provide permissions through Windows Firewall if applicable
• If the guest OS is Vista/2008 or later:
  • In the Network and Sharing Center, verify that it is not set for a public domain.
  • Verify that the Remote Registry Service is started.

Note: As of 9.5 and later we have guest interaction proxies that deploy components: https://helpcenter.veeam.com/docs/backup/vsphere/guest_interaction_proxy.html?ver=95