I'm sharing some knowledge.
I was trying to download some GPG encrypted .txt files from an FTP (using Attachmate Reflection FTP) and then decrypt them. I kept receiving the error 'Decryption Failed: No Data'
When I clicked on the hyperlink for 'Diagnostics' I saw the following 'indeterminate length for invalid packet type...'
The problem was not GPG, but something with my FTP Client.
I solved my problem by going to Tools in the FTP Client and changed 'Transfer Method' from 'SMART' to 'Binary'