I think you should try:
I used %matplotlib inline in the first cell of the notebook and it works.
%matplotlib inline
import matplotlib
import numpy as np
import matplotlib.pyplot as plt
You can also always start all your IPython kernels in inline mode by default by setting the following config options in your config files:
c.IPKernelApp.matplotlib=<CaselessStrEnum>
Default: None
Choices: ['auto', 'gtk', 'gtk3', 'inline', 'nbagg', 'notebook', 'osx', 'qt', 'qt4', 'qt5', 'tk', 'wx']
Configure matplotlib for interactive use with the default matplotlib backend.
Try this i hope this would work.