DataGrid InLine Editing is not working

Dear Radzen Team,
I creat an inline editing DataGrid (at not the first time) but I do not know why I cannot add or edit rows.
When I click the New row button nothing happens just disapear the existing rows nd it happens when I click the edit (pencil) button, too.
I knew I made a mistake somewhere but I do not know where.
Could you help me, please?

public class VoucherDto : BaseDto
{
    public VoucherDto()
    {
        AssetItems = new List<VoucherItemDto>();
    }
   
    ...
    ...

    public List<VoucherItemDto> AssetItems { get; set; }
}
protected VoucherDto VoucherDto { get; set; }
protected override async Task OnInitializedAsync()
{
    await base.OnInitializedAsync();
    VoucherDto = new VoucherDto();
}

protected VoucherItemDto voucherItemToInsert;
protected VoucherItemDto voucherItemToUpdate;

protected async Task InsertRow() 
{
    voucherItemToInsert = new VoucherItemDto();
    voucherItemToInsert.Quantity = 1;
    voucherItemToInsert.QualityId = 11;
    await assetsGrid.InsertRow(voucherItemToInsert);
}
<RadzenDataGrid @ref="assetsGrid" EditMode="DataGridEditMode.Single" EmptyText="No data." Count="@count" Data="@VoucherDto.AssetItems" TItem="VoucherItemDto" RowUpdate="@OnUpdateRow" RowCreate="@OnCreateRow" Density="Density.Compact">
  <Columns>
    <RadzenDataGridColumn TItem="VoucherItemDto" Property="VoucherItemDto.Quantity" Title="Mennyiség (db)">
      <EditTemplate Context="voucherItemDto">
         <RadzenNumeric Min="1" ShowUpDown="false" @bind-Value="voucherItemDto.Quantity" Style="width:100%; display: block" Name="Mennyiseg" />
         <div class="rz-messages-error @quantityValidatorWarning">Wrong quantity.</div>
      </EditTemplate>
    </RadzenDataGridColumn>
    <RadzenDataGridColumn TItem="VoucherItemDto" Context="voucherItemDto" Filterable="false" Sortable="false" TextAlign="TextAlign.Right" Width="156px">
      <Template Context="voucherItemDto">
        <RadzenButton Icon="edit" ButtonStyle="ButtonStyle.Light" Variant="Variant.Flat" Size="ButtonSize.Small" Click="@(args => EditRow(voucherItemDto))" @onclick:stopPropagation="true">
        </RadzenButton>
        <RadzenButton ButtonStyle="ButtonStyle.Danger" Icon="delete" Variant="Variant.Flat" Shade="Shade.Lighter" Size="ButtonSize.Small" Class="my-1 ms-1" Click="@(args => DeleteRow(voucherItemDto))" @onclick:stopPropagation="true">
        </RadzenButton>
      </Template>
      <EditTemplate Context="voucherItemDto">
        <RadzenButton Icon="check" ButtonStyle="ButtonStyle.Success" Variant="Variant.Flat" Size="ButtonSize.Small" Click="@((args) => SaveRow(voucherItemDto))">
        </RadzenButton>
        <RadzenButton Icon="close" ButtonStyle="ButtonStyle.Light" Variant="Variant.Flat" Size="ButtonSize.Small" Class="my-1 ms-1" Click="@((args) => CancelEdit(voucherItemDto))">
        </RadzenButton>
      </EditTemplate>
    </RadzenDataGridColumn>
  </Columns>
</RadzenDataGrid>

I'm sorry to bother you. I found the cause of my problem. I left the Count property in the DataGrid. Unfortunately, there wasn't any error message just the grid simply did not work.