Not Able to add a custom script extension for Linux vm - azure

Question

I have a linux Cent OS vm and am trying to add a custom script to it. If i do it manually from the portal i am able to install the custom script extension for linux. But i am not able to install the custom script via powershell code that i added below. Need some help on it. I am storing the custom script file in a storage account and calling it from there when installing the custom script extension on Linux.
Error i get is : Enable failed: processing file downloads failed: failed to download file[0]: failed to download file: unexpected status code: actual=404 expected=200
if($vmname.OSType -eq "Linux"){
$resourcegroup=$vmname.ResourceGroupName
$location=$vmname.Location
$vm=$vmname.Name
$TheURI = "https://storageaccount.blob.core.windows.net/container/cstmscript.sh"
$ScriptSettings = #{"fileUris" = #($TheURI); "commandToExecute" = "sh cstmscript.sh";}
Set-AzVMExtension -ResourceGroupName $resourcegroup -VMName $vm -Name "Custom Script" -Publisher "Microsoft.Azure.Extensions" -TypeHandlerVersion 2.0 -ExtensionType "CustomScript" -Location $location -Settings $ScriptSettings
}
Cant use Set-AzVMCustomScriptExtension as that's for only Windows VM's

Answer 1

Thanks Satya It did work Btw . I needed to add the access keys.
here is the code
if($vmname.OSType -eq "Linux"){
$resourcegroup=$vmname.ResourceGroupName
$location=$vmname.Location
$vm=$vmname.Name
$TheURI = "https://storage.blob.core.windows.net/container/cstmscript.sh"
$ScriptSettings = #{"fileUris" = #($TheURI); "commandToExecute" = " sh cstmscript.sh";}
$ProtectedSettings = #{"storageAccountName"="storage";"storageAccountKey" = ""};
Set-AzVMExtension -ResourceGroupName $resourcegroup -VMName $vm -Name "Custom Script" -Publisher "Microsoft.Azure.Extensions" -TypeHandlerVersion 2.0 -ExtensionType "CustomScript" -Location $location -Settings $ScriptSettings -ProtectedSettings $ProtectedSettings
}

Answer 2

I had tried hitting the above the url
https://storageaccount.blob.core.windows.net/container/cstmscript.sh
Which is more or less 404 error as encountered below :
Enable failed: processing file downloads failed: failed to download file[0]: failed to download file: unexpected status code: actual=404 expected=200
Looks like you re not able to access the cstmsscript.sh & encountering a 404 - you will have to host the file anonymously accessible or alternatively use means to grant access ( like SAS )