Powershell giving error for invoke rest method but works in powershell

Question

I have been working on a script that essentially creates a user using an API. It takes a list of active directory users and creates account on the second software using the API using invoke method. Now the problem is that it will go through for some of them while give error 400 for others saying the required field is missing so i logged the body of failed requests and tried them with postman they work correctly. I can't understand this behavior and if there is any way around it.

Function CreatePhishUser($user){
        
               
            if($user.PreferredLanguage -eq $null)
                {
                Write-Output "heh"
                   $body = @{
                    "id"= "somethingsomething"; #English
                   "target"= @{
                        "email"= $user.emailaddress;
                        "first_name"= $user.GivenName;
                        "last_name"= $user.Surname;
                        "company"= $user.Company;
                        "title"= $user.Title;
                        "address_one"= $user.StreetAddress;
                        "city"= $user.City;
                        "state"= $user.State;
                        "zip"= $user.PostalCode;
                        "country"= $user.Country;
                        "phone_business"= $user.OfficePhone;
                        "phone_business_fax"= $user.Fax;
                        "phone_mobile"= $user.telephoneNumber;
                        "language"= "en";
                        "department"= $user.Department;
                        "manager"= "hello";
                        "is_active"= 1;
                        "groups" = @{
                            "id"="something something9";
                            "name"="English"
                            
                       
                       
                       }
                    }
                    }
             }else {
                        $body = @{
                        "id"= "somethingsomething";  #French
                       "target"= @{
                            "email"= $user.emailaddress;
                            "first_name"= $user.GivenName;
                            "last_name"= $user.Surname;
                            "company"= $user.Company;
                            "title"= $user.Title;
                            "address_one"= $user.StreetAddress;
                            "city"= $user.City;
                            "state"= $user.State;
                            "zip"= $user.PostalCode;
                            "country"= $user.Country;
                            "phone_business"= $user.OfficePhone;
                            "phone_business_fax"= $user.Fax;
                            "phone_mobile"= $user.telephoneNumber;
                            "language"= "fr";
                            "department"= $user.Department;
                            "manager"= "hello";
                            "is_active"= 1;
                            "groups" = @{
                            "id"="something something";
                            "name"="French"
                            
                       
                       
                       }
                        }
                      }



                }


        $jsonBody = $body | ConvertTo-Json
        Write-Output $jsonBody
        #create user 
      
          $response = Invoke-RestMethod -URI somelink/somelink  -
ContentType "application/json" -Method  Post  -Headers @{"api-token" = $token}   -Body $jsonbody
          
}
CreatePhishUser($aduser)

Thanks :)