Missing data in Boxplot using matplotlib

Question

The original dataset contain 4 data named df1,df2,df3,df4(all in pandas dataframe format)

df1 = pd.read_csv("./df1.csv")
df2 = pd.read_csv("./df2.csv")
df3 = pd.read_csv("./df3.csv")
df4 = pd.read_csv("./df4.csv")
    # Concat these data 
dataset = [df1,df2, df3,df4]


# Plottting 
fig = plt.figure()
bpl = plt.boxplot(dataset, positions=np.array(xrange(len(dataset)))*2.0-0.4, \
                          sym='+', widths=0.5, patch_artist=True)

plt.show()

But the first data df1 was missing. I check df1, find nothing abnormal.

I upload these 4 data here in .csv format.
Any advice would be appreciate!

Update

Answer 1

I could make the plot without any problem.