Get-WmiObject : The RPC server is unavailable

I am getting the following error when I tried to get disk size information from the server. The script that I am using runs fine against my other 62 SQL servers however it is failing to connect to 3 of them. I do not believe it is my powershell script I think it has something to do with the server but I am not sure where to look.

Get-WmiObject : The RPC server is unavailable. (Exception from HRESULT: 0x800706BA)At F:\SQL_DB_SIZES\Disk Space 
Report.ps1:178 char:8
+  $dp = Get-WmiObject win32_logicaldisk -ComputerName $server |  Where-Object {$_ ...
+        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [Get-WmiObject], COMException
    + FullyQualifiedErrorId : GetWMICOMException,Microsoft.PowerShell.Commands.GetWmiObjectCommand

Where do I start to trouble shoot this? I am assuming at the target server but I am not sure where to look.