Zero Rated GST ASMT10 - Goods and Services Tax - GST

So, I have foreign e-commerce income in the form of digital products and Payments do come in USD which is then converted by the bank in INR. I have been under the impression that export of OIDAR services are zero rated for GST therefore I have been filing Nil returns all this time and I had no idea about the existence of LUT until recently I got a ASMT10 notice asking to explain the Nil returns filed since there were some TCS deductions. I'm not sure how to take things from here so any advice is welcome. Thanks