There might be several reasons to disable client authorization check on Veeam Monitor Server:
NOTE: For the instructions to work, authorization has to take place on Windows level. This requires identical accounts with identical passwords to be created on Veeam One Server and Veeam Monitor Client machines if Veeam One is used in a workgroup. Additionally if the registry key noted above is not listed manually create as noted or contact support for assistance.
If these instructions do not help, the problem might be in security limitations of cross-domain network communications. Before running Veeam Monitor Client, use the following command to pre-establish network connection between the two servers:
net use \\your_monitor_server
You might be asked for security credentials. As a result, the network connection will be established between the Veeam Monitor Server and Veeam Monitor Client workstation. Run the Client to make sure it works.
Please note that disabling Client Authorization is an unsecure way to resolve the problem. Anyone who has Veeam Monitor Client installed would be able to connect to your Veeam Monitor Server, change settings or use remote connection to the virtual machines in your environment via the Console tab.
If you have any questions or problems, please contact Veeam Support at http://www.veeam.com/support