Frame is not showing in windows

Question

I am transitioning to .Maui from forms

I developed a simple app, but on Windows, it looks horrible

this is the same on Android

XAML code

<?xml version="1.0" encoding="utf-8" ?>  
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"  
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"  
             x:Class="ColorPicker.MainPage">  
  
    <ContentPage.Resources>  
        <Color x:Key="Primary">#ab3527</Color>  
        <Color x:Key="Secondary">#775752</Color>  
        <Color x:Key="Tertiary">#705c2e</Color>  
    </ContentPage.Resources>  
  
    <Grid RowDefinitions="*,Auto"  
          x:Name="MyGrid">  
        <Border Grid.Row="2"  
                Background="#ffff"  
                StrokeThickness="4">  
            <Border.StrokeShape>  
                <RoundRectangle   
                                CornerRadius="20" />  
            </Border.StrokeShape>  
            <VerticalStackLayout Padding="15"  
                                 Spacing="15">  
                  
                <Label FontAttributes="Bold"  
                       FontSize="Large"  
                       TextColor="Black"  
                       HorizontalTextAlignment="Center"  
                       VerticalTextAlignment="Start"  
                       Text="Color Maker" />  
                  
                <Label Text="Red Value:"  
                       TextColor="Red" />  
                  
                <Slider x:Name="redSlider"  
                        ValueChanged="Slider_ValueChanged"  
                        ThumbColor="PaleVioletRed"  
                        MaximumTrackColor="{StaticResource Tertiary}"  
                        MinimumTrackColor="{StaticResource Secondary}" />  
                  
                <Label Text="Green Value:"  
                         
                       TextColor="Green" />  
                <Slider x:Name="greenSlider"  
                        ValueChanged="Slider_ValueChanged"  
                        ThumbColor="PaleVioletRed"  
                        MaximumTrackColor="{StaticResource Tertiary}"  
                        MinimumTrackColor="{StaticResource Secondary}" />  
                  
                <Label Text="Blue Value:"  
                       TextColor="Blue" />  
                  
                <Slider x:Name="blueSlider"  
                        ValueChanged="Slider_ValueChanged"  
                        ThumbColor="PaleVioletRed"  
                        MaximumTrackColor="{StaticResource Tertiary}"  
                        MinimumTrackColor="{StaticResource Secondary}" />  
  
                <Frame CornerRadius="20">  
                    <Grid ColumnDefinitions="*,*,Auto">  
                          
                        <Label Text="Hex Value"  
                               HorizontalTextAlignment="Start"  
                               VerticalTextAlignment="Center"  
                               TextColor="Black" />  
                          
                        <Label Grid.Column="1"  
                               x:Name="lblHex"  
                               HorizontalTextAlignment="End"  
                               TextColor="Black"  
                               VerticalTextAlignment="Center"  
                               Text="#000000" />  
  
                        <ImageButton HeightRequest="25"  
                                     Source="copy"  
                                     Clicked="ImageButton_Clicked"  
                                     Grid.Column="2"  
                                     VerticalOptions="Center"/>  
                    </Grid>  
                </Frame>  
                <Button BackgroundColor="{StaticResource Blue100Accent}"   
                        Text="Get a random value"   
                        x:Name="RandomBbn"  
                        Clicked="RandomBbn_Clicked"  
                        TextColor="White" />  
            </VerticalStackLayout>  
        </Border>  
    </Grid>  
</ContentPage>