Blazor Base Class Parameter not binding to TextEdit

I have a Base class for an Add/Edit form

public partial class BaseAddForm<TInput, TOutput> : ComponentBase    where TInput : BaseModel, new()    where TOutput: BaseModel, new()

In this base I have the [Parameter]

    [Parameter]    public TInput Input { get; set; }

In the drived class (which is using Blazorise compoents) I then bind as follows;

<Validation Validator="@ValidationRule.None"><Field Horizontal="true" ColumnSize="ColumnSize.Is6.OnDesktop"><FieldLabel ColumnSize="ColumnSize.Is3.OnDesktop">Group</FieldLabel><FieldBody ColumnSize="ColumnSize.Is9.OnDesktop"><TextEdit @ref="companyGroupTextBox" @bind-Text="@Input.Group" Placeholder="Enter the Company Group Name.."></TextEdit></FieldBody></Field>

However, the field is appearring as blank when rendering (even though Input has values).

In the derived class .cs OnInitializedAsync() I have (redcued for brevity);

    protected override async Task OnInitializedAsync()    {        Test = Input;        if (Input.Address == null)        {            Input.Address = new CompanyAddressInputModel();        }        if (Input.Contacts != null)        {            var primaryContact = Input.Contacts.FirstOrDefault(x => x.IsPrimaryContact);            if (primaryContact != null)            {                InputMainContact = primaryContact;            }        }        await RefreshBusinessTypesAsync();        await GetCompanyPositionsAsync();        await base.OnInitializedAsync();    }</Validation>

If you note I have Test = Input as a test and if I then;

<Validation Validator="@ValidationRule.None"><Field Horizontal="true" ColumnSize="ColumnSize.Is6.OnDesktop"><FieldLabel ColumnSize="ColumnSize.Is3.OnDesktop">Group</FieldLabel><FieldBody ColumnSize="ColumnSize.Is9.OnDesktop"><TextEdit @ref="companyGroupTextBox" @bind-Text="@Test.Group" Placeholder="Enter the Company Group Name.."></TextEdit></FieldBody></Field></Validation>

The Test.Group value appears?

For completness in the base class I have tried the following to trigger the chang ein state to update;

protected override async Task OnInitializedAsync(){    _isInitialized = true;    await ResetAsync();}protected override async Task OnAfterRenderAsync(bool firstRender){    if (firstRender)    {        _isInitialized = true;        await ResetAsync();    }}public void Dispose(){    _isInitialized = false;}public virtual async Task ResetAsync(){    try    {        if (InputModelPreSetData != null)        {            Input = InputModelPreSetData.DeepCopy();        }        else        {            Input = new TInput();        }        if (!renderHandle.IsInitialized)        {            //not intialised so return to avoid an error            return;        }        if (FormValidations == null)        {            FormValidations = new Validations();        }        else        {            await FormValidations.ClearAll();        }    }    catch(Exception ex)    {        _logger.LogError(ex, $"Error in ResetAsync '{ex.Message}'");    }    finally    {        StateHasChanged();    }}

Can anyone tell me why Blazor doesn't seem to be picking up the change in state on the base model parameter please?