To simply show the map, all you need to do is
What your code is doing, however, is assigning the output of the plot function to the variable ax, but not actually calling that output to see it. If all you want is to see the plot, you can call that variable in its own cell.
If, however, you're trying to create a MatPlotLib figure with the map in it, there's a different way. Note in the GeoPandas documentation for the plot function the parameter ax. This parameter indicates that you want your plot assigned to MatPlotLib axes; you should already have one established.
Try something like this:
fig1, ax1 = plt.subplots(1, 1, figsize=(6,6)) aus_poas.plot(ax=ax1) plt.show()