Hi @kjaques
so the data is loaded but it is not showing up in the visual? There is no issue with uploading the data, the newly added month JAN is showing up but not in the way you expect. 
The new month has the date in a different format than the rest of the rows. Why? Not sure unless I see the data. One thing you can try: In excel create another DATE column and populate it with the dates from the date column but make sure the column uses a consistent date format down all rows. Or try anything that ensures you have the same date format in the original date column.
Hope it helps,
GL