Plotly Library Do Not Showed Anything

I don't have the chart_studio installed but it seems it wasn't used anyway in your code. So after commenting chart_studio import and adding some data to your dataframe I can successfully run your code in my IDE (Eclipse). However it was opening two windows with the same plot so I had to remove one of the two last lines so just one window opens.

Then I tried your code in local Jupyter Notebook and in hosted Google CoLab and it works fine with the following code:

import plotly.graph_objs as go
import pandas as pd
import numpy as np

rng = pd.date_range('2015-02-24', periods=5, freq='T')
df = pd.DataFrame({ 'date': rng, 'qty': np.random.randn(len(rng)) }) 

#plot monthly sales
plot_data = [
    go.Scatter(
        x=df['date'],
        y=df['qty'],
    )
]

plot_layout = go.Layout(
        title='Montly Sold'
    )
fig = go.Figure(data=plot_data, layout=plot_layout)
fig.show()

Or you could leave the import plotly.offline as pyoff and use pyoff.iplot(fig) instead of fig.show() which also works fine.

Note: Running your code in Jupyter Notebook for the first time after (re-)starting you computer can take quite some time to generate and show a plot.