GridPanel cannot display value using SQL datasource

[finn.du]

This is my gridpanel control code.

<ext:GridPanel
ID="GridPanel1_SDEServer"
runat="server"
Title="Public SDE Server"
AutoHeight = "true">
<Store>
<ext:Store ID="Store_SDESERVER" runat="server">
<Reader>
<ext:JsonReader>
<Fields>
<ext:RecordField Name="server" />
<ext:RecordField Name="status"/>
<ext:RecordField Name="instance" Type="String" />
<ext:RecordField Name="sdatabase"/>
<ext:RecordField Name="dbms" />
<ext:RecordField Name="os"/>
</Fields>
</ext:JsonReader>
</Reader>
</ext:Store>
</Store>
<ColumnModel>
<Columns>
<ext:Column DataIndex="server" Header="Server" />
<ext:Column DataIndex="status" Header="Status" />
<ext:DateColumn DataIndex="instance" Header="Instance" />
<ext:DateColumn DataIndex="sdatabase" Header="Database" />
<ext:Column DataIndex="dbms" Header="DBMS" />
<ext:Column DataIndex="os" Header="OS" />
</Columns>
</ColumnModel>
<SelectionModel>
<ext:RowSelectionModel ID="RowSelectionModel1" runat="server" />
</SelectionModel>
</ext:GridPanel>

I dynamically add a sqldatasource in a button click event.

And some data is not displayed. See:


And I used the same selection command in SQL server: