RE: Released Products V2 Import error
In my case I've also encountered this issue due to line ending characters (as well as many of the suggestions already answered by others in this thread). Ensure that there are no blank rows at the end of your file, and that it does not contain incorrect values which can often be the case when using tab or csv files that can contain these characters in description- or note fields.
A combination of excel and notepad++ usually works for me to root out the cause. Recently I found a new issue so it might help anyone stumbling upon this thread:
Use notepad++ and ensure to show all characters (or in this case it's sufficient with line ending but better to show all).

Check if line endings are in cr ln format, if so try to change to unix format instead:

Via Edit menu - EOL conversion, select Unix

Check that line endings are now only linefeed:

Save and try again, this resolved the final issue I had with a specifically troublesome file after first removing duplicates and empty rows at the bottom, hopefully it can help.