You may find instances where you receive an import file that has mutliple line items but when you preview the import it appears that there is only one order.  There are a few things that can cause this. The first is that there's no CRLF at the end of each order (carriage return line feed). Another little tidbit we found lately is below.

Is your FTP setup for ASCII or Auto transfer mode? If the sender's system is UNIX-based, text files are stored with LF delimiters (not CRLF, like non-UNIX systems). However, if you transfer in ASCII mode, your resulting file will have CRLF delimiters as you need.

If the FTP client that you're using allows you to set the Transfer mode to ASCII, Binary or Auto (based on file extension) please do the following. If yours is set to Binary, you'll want to change it to either ASCII or Auto -- and if you use Auto, you'll need to be sure that your program knows that files with .csv extension should be transferred in ASCII mode. (The list of file extensions is another setting you should be able to edit, somewhere in your FTP client program.)