Dash Table not showing up at all

Dash Python
1

I try to create a simple dash_table but its show up nothing. I load a dataframe and uses this code:

html.Div([dash_table.DataTable(
                            id='datatable',
                            data=df.to_dict('row'),
                            row_selectable=False,
                            filtering=True,
                            sorting=True,
                            editable=False,
                            #style_as_list_view=True,
                            style_table={'height': '300','overflowX': 'scroll'},
                            n_fixed_rows=1,

                         style_header={'backgroundColor': 'rgb(30, 30, 30)'},
                         style_cell={
                             'backgroundColor': 'rgb(50, 50, 50)',
                             'color': 'white'
                         },


                        )]

In a callback upload function which is also connected with a graph I do this:

@app.callback(
Output('datatable', 'data')
,#Output('seabornScatterMatrix','figure')
[Input('upload', 'contents')],
[State('upload', 'filename')])

def update_figure(content,filenameList):
#dcc.Storage(id='session', storage_type='session'),
#if content or filenameList is None:
#    raise PreventUpdate
fullDf = pd.DataFrame()
if not content:
    return [{'test':1}]
for table, fileName in zip(content, filenameList):
    try:
        if '.csv' in fileName:
            content_type, content_string = table.split(',')
            decoded = base64.b64decode(content_string)
            df = pd.read_csv(io.StringIO(decoded.decode('utf-8')), sep='\t')
        elif 'xls' in fileName:
            df = pd.read_excel(io.BytesIO(decoded))
    except Exception as e:
        print(e)
        return html.Div(['There was an error processing this file.'])
    fullDf = pd.concat([fullDf, df])

fullDfDict = fullDf.to_dict('rows')#'index'
#print(fullDfDict)
#fullDf=functions.factorize(fullDf)


#figure = sns.pairplot(data=fullDf[['ContactIssue', 'GripperMark', 'DarkDefaultArea', 'SysInfoSystemNo']],
#                      hue='SysInfoSystemNo')
#print(figure)

return fullDfDict

The thing is, with dash_table experiments and the output “rows” it works! Why is that?