What might be the reason of the 53 exception during 'Visual Studio Test Agent Deployment' step - testing

Question

Currently I'm trying to use tfs 2015 and vNext build system. There is this exception during 'Visual Studio Test Agent Deployment' step, and I'm not really sure what to do.
What might cause this exception:
Executing the powershell script: ...\DeployTestAgent.ps1
DistributedTests: Starting to deploy and configure test agent on test machines.
DistributedTests: Inputs provided are:
DistributedTests: Machines:
DistributedTests: Username: ...\...
DistributedTests: Machine Group name: Tracker Test Machines
DistributedTests: Run as process: False
DistributedTests: Login Automatically: False
DistributedTests: Disable Screen saver: False
DistributedTests: Agent location: C:\Distr\vstf_testagent.exe
DistributedTests: Update test agent: True
DistributedTests: Run test agent as DataCollection only : False
DistributedTests: Path to script that installs test agent on remote machine: ...\TestAgentInstall.ps1
DistributedTests: Path to script that configures test agent on remote machine: ...\TestAgentConfiguration.ps1
DistributedTests: Path to script that downloads test agent on azure remote machines : ...\DownloadTestAgent.ps1
DistributedTests: Path to script that checks if test agent is installed on remote machine: ...\CheckTestAgentInstallation.ps1
DistributedTests: Test Agent is being copied to: ...\Temp\3bc272a1-3cc0-479e-aff8-84483e1f6ad8\vstf_testagent.exe
DistributedTests: Task 'CopyFilesToTestAgent' on machine '...:5985' is being run
DistributedTests: Task 'CopyFilesToTestAgent' on machine '...:5985' completed.
DistributedTests: Task 'CopyFilesToTestAgent' for machine ...:5985's Error : System.AggregateException: Failed to execute the powershell script. Consult the logs below for details of the error.
Failed to connect to the path \\... with the user .\... for copying.System error 53 has occurred.
The network path was not found.
---> System.Management.Automation.RuntimeException: Failed to connect to the path \\... with the user .\... for copying.System error 53 has occurred.
The network path was not found.
---> System.Management.Automation.RuntimeException: Failed to connect to the path \\... with the user .\... for copying.System error 53 has occurred.
The network path was not found.
--- End of inner exception stack trace ---
at System.Management.Automation.Runspaces.PipelineBase.Invoke(IEnumerable input)
at System.Management.Automation.PowerShell.Worker.ConstructPipelineAndDoWork(Runspace rs, Boolean performSyncInvoke)
at System.Management.Automation.PowerShell.Worker.CreateRunspaceIfNeededAndDoWork(Runspace rsToUse, Boolean isSync)
at System.Management.Automation.PowerShell.CoreInvokeHelper[TInput,TOutput](PSDataCollection`1 input, PSDataCollection`1 output, PSInvocationSettings settings)
at System.Management.Automation.PowerShell.CoreInvoke[TInput,TOutput](PSDataCollection`1 input, PSDataCollection`1 output, PSInvocationSettings settings)
at System.Management.Automation.PowerShell.Invoke(IEnumerable input, PSInvocationSettings settings)
at Microsoft.VisualStudio.Services.DevTestLabs.Deployment.Deployment.PowershellExecutor.<>c__DisplayClass26_0.<Invoke>b__0()
at Microsoft.VisualStudio.Services.DevTestLabs.Deployment.RetryExecutor.<>c__DisplayClass19_0`1.<Execute>b__0()
at Microsoft.VisualStudio.Services.DevTestLabs.Deployment.RetryExecutor.Execute(Action action)
at Microsoft.VisualStudio.Services.DevTestLabs.Deployment.RetryExecutor.Execute[T](Func`1 action)
at Microsoft.VisualStudio.Services.DevTestLabs.Deployment.Deployment.PowershellExecutor.Invoke(String errorContextMessage, Boolean writeResultToLog, Boolean isCancellable)
--- End of inner exception stack trace ---
...
Other remote powershell scripts seem to run without troubles. Not sure what it might be.
As usual, don't hesitate to ask for additional information.

Answer 1

Looks like you need to enable file sharing:
In this specific situation the RoboCopy tool is complaining that the
network path was not found, because I forgot to enable file sharing on
the target machine. Once I enabled file sharing an running again the
build everything was green, and I can verify that all files were
correctly copied on target machines.
http://www.codewrecks.com/blog/index.php/2015/06/20/build-vnext-support-for-deploying-bits-to-windows-machines/

Answer 2

I just had a similar issue and the problem was that I had to enable certain rules in the Windows Firewall that the Filesharing works.
I tested it by disabling the firewall completly and then just try to connect through the Windows Explorer to this FileShare via "\MachineName"
As soon as this worked, this error was gone as well.
After this I reenabled the Firewall again and tried to figure out the rules that have to be added.
In the Advanced Firewall settings are some rules regarding File and Printer Sharing that are disabled, I enabled those and that made it work.
Hope this helps