Not sure if this applies here or not, but I was having this issue when downloading credit card transactions past a certain point in time that were automatically imported. I had to download it as a CSV file, but then they were trying to post as credits in the account rather than expenses. I went back to the file and made sure all the amounts were listed as negatives, but that didn't make a difference until I went back and made sure my download was "saved as" a CSV UTF 8 (Comma Delimited) format... then it uploaded correctly and saved me a lot of time manually entering each transaction.