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Hello - TT Online 2019 asks specifically for a PDF file however. I uploaded the 2018 1040 PDF file which was generated by TT Desktop 2018 itself, and it says "Upload error" with no other explanation.

When I try to contact TT Help, it dead ends because I haven't started my return. Talk about a horrible user experience... What am I doing wrong here? I am uploading TT's own generated 1040 file.