Spreadsheet not sorting or filtering

[Pamipj]

I have a monthly spreadsheet that will not filter or sort by date.  The column is in date format, the numbers are not imported, I have cleared all filters.  All of the other months I have had no problem, but October will not sort.  I copied the page to a new document and it still won't sort.  Any ideas?

[#2]

@Pamipj 

Please check if you actually have dates, not texts. To apply date format is not enough if you have texts, texts shall be converted to dates. You may test by =ISTEXT(A1) or like from any empty cell.