Did you read those letters carefully? What do the instructions in the letters tell you to do? Do the letters say anything about "uploading" documents? Or do the letters instruct you to mail or fax some information, and/or to call the IRS?
https://www.irs.gov/individuals/understanding-your-letter-12c
https://www.irs.gov/individuals/understanding-your-letter-4883c
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
