There should be an appropriate amount of padding at the top of the chart:

0
500000
1.00e+6
1.50e+6
2.00e+6
2.50e+6
3.00e+6
06Dec
13Dec
20Dec
27Dec
03Jan
10Jan
17Jan
24Jan

The second series (which is entirely zero) should be visible, and the y-axis should go down to zero.

0
2000
4000
6000
8000
10000
12000
14000
16000
15Oct