Hello Ashfaq,
Although I am not 100% sure if this can be reason for the problem faced by you : Unable to get "Total Demand" key figure in data extraction. But you can recheck and make sure -
'Total Demand' Key figure in SNP Planning area is an AUXILIARY key figure. (not the Standard Order or Timeseries Key figure). Auxiliary key figures are used when u want to perform some calculations (mainly used in macro) and it store values for temporarily.
Hope this will give you some clue.
Thank you
Satish Waghmare