How to respond for intimation u/s 139(9)

For the AY 2020-21, for my client who has Income from bank kiosk, common service center & insurance commission I have filed under "Non specified profession - without books of accounts" (obviously without balance sheet and p&l)
Recently he received a defective notice that "as per the provisions of Sec.44AA, the taxpayer is required to maintain books of accounts. However, as seen from the return, the taxpayer has not filled up Part A of the Profit and Loss Account and Balance Sheet. Further, income from business has not been offered under presumptive taxation, if eligible" and asking to submit a balance sheet and P&L.
This is how I have been filing for him for the past 3 years and we have never had this issue before. My client's income is less than 4 lakhs.  
Wondering how and why this popped up.  
Please suggest what to do..