Adding Sharepoint user remotely PowerShell script - sharepoint

Question

Running EnsureUser on an existing domain account give an error that the user could not be found. Same command(s) works fine in PowerShell on SharePoint server locally. I am able to create a SharePoint group remotely, just can't add a user to that group.
$site = new-object Microsoft.SharePoint.SPSite("http://sharepoint.company.com/dev")
$web = $site.OpenWeb()
function GrantUserpermission($userName)
{
$folder.BreakRoleInheritance("true")
$web.SiteGroups.Add("test_group", $web.Site.Owner, $web.Site.Owner, "Desc")
$ownerGroup = $web.SiteGroups["test_group"]
$ownerGroup.AllowMembersEditMembership = $true
$ownerGroup.Update()
$sitename = Get-SPWeb http://sharepoint.company.com/dev
$EnsuredUser = $sitename.EnsureUser("domain\user")
Set-SPUser -Identity $EnsuredUser -web $sitename -group "test_group"
$AddGroup = $web.SiteGroups["test_group"]
$roleAssignment = new-object Microsoft.sharepoint.SPRoleAssignment($AddGroup)
$roleDefinition = $web.RoleDefinitions["Contribute"]
$roleAssignment.RoleDefinitionBindings.add($roleDefinition)
$folder.RoleAssignments.Add($roleAssignment)
$folder.SystemUpdate()

Answer 1

Check if the domain user exists before use the EnsureUser method.
If you want to add SharePoint user to group in remote server, we can use CSOM with PowerShell to achieve it.
$url="http://sharepoint.company.com/dev"
$userName="administrator"
$password="**"
$domain="test"
$sGroup="test_group"
$sUserToAdd="domain\user"
$ctx = New-Object Microsoft.SharePoint.Client.ClientContext($url)
$credentials = New-Object System.Net.NetworkCredential($userName,$password,$domain)
$ctx.Credentials = $credentials
$groups=$ctx.Web.SiteGroups
$ctx.Load($groups)
#Getting the specific SharePoint Group where we want to add the user
$group=$groups.GetByName($sGroup)
$ctx.Load($group)
#Ensuring the user we want to add exists
$user = $ctx.Web.EnsureUser($sUserToAdd)
$ctx.Load($user)
$userToAdd=$group.Users.AddUser($user)
$ctx.Load($userToAdd)
$ctx.ExecuteQuery()