Add multiple AD users in multiple groups - Split Excell cell

Hi Guy's and hello from Paris !

I'm just starting to learn Powershell and...

I'm try to write a script to add multiple users in multiple group, and I have a problem to split an Excell cell.
I have a special conditon, This script will run via System Center Orchestrator. And, I'm need no error during the execution...

I hope you can help me...

My csv file exemple :
users;groups
testuser01;GGU_TestU,GGU_TestA,GGU_TestS,GGU_TestP,GGU_TestI
testuser02;GGU_TestU,GGU_TestA,GGU_TestS,GGU_TestP,GGU_TestI
testuser03;GGU_TestU,GGU_TestA,GGU_TestS,GGU_TestP,GGU_TestI

My script :

$csvfile = Import-Csv -path "C:\tests.csv" -delimiter ';'

    foreach($item in $csvfile) {
   
        $ACN = $item.users
        $NDGS = $item.groups.split(',')
       
      
       $verifmembers = Get-ADGroupMember -Identity $NDGS }

                
           foreach ($NDG in $NDGS) {
          
            if ($verifmembers -notcontains $NDG) {
            Add-ADGroupMember $NDG -Members $ACN
           }
        }


Error :

Get-ADGroupMember : Cannot convert 'System.String[]' to the type 'Microsoft.ActiveDirectory.Management.ADGroup' required by parameter 'Identity'. Specified method
is not supported.
At C:\test1.ps1:11 char:52
+        $verifmembers = Get-ADGroupMember -Identity $NDGS }
+                                                    ~~~~~
    + CategoryInfo          : InvalidArgument: (:) [Get-ADGroupMember], ParameterBindingException
    + FullyQualifiedErrorId : CannotConvertArgument,Microsoft.ActiveDirectory.Management.Commands.GetADGroupMember




Any help would be greatly appreciated ! Thanks for your time and help

And sorry for my poor english...