I just copied your entire lookup in the image and tried this myself by creating a .csv.
I don't have zeros in all rows and so it seems that your csv is not well formatted. Can you try what I just did?
Create a csv in a plaintext file:
_time,image_name,os_name
10/01/2018, azure1, CentOS7
10/02/2018, azure1, CentOS7
15/02/2018, azure1, CentOS7
20/02/2018, azure3, CentOS7
10/03/2018, azure3, CentOS7
11/03/2018, azure2, CentOS7
12/03/2018, azure2, CentOS7
Save it like this and to csv_timechart.csv, put it in the lookup folder of the app you are using, and run the command I told you.
Feed us back please
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