Hi Niteen -
I see you are only loading data until 2017-sep. If you won't have oct, nov, and dec in you app, they won't get calculated. Now this may be how it is only in the sample app, whereas your original app might have it. But this would be a good starting point to check. Do you even have those three months in your application or not?
Just concatenate those three into your main field
"INC Closed Time"
FROM [lib://Downloads/Ticket Forecasting Problem.xlsx]
(ooxml, embedded labels, table is Sheet1);
LOAD Date(Date#("INC Closed Time", 'DD/MM/YYYY')) as "INC Closed Time"
INC Closed Time