I have a table of data with positive and negative numbers in column
B. Row 1 is a "title" row; but in fact, all cells are blank. I
select all the columns and enable AutoFilter. The selection buttons
are in Row 1, as expected.

But when I click on the column B button and select Sort Ascending, it
appears that Row 2 is not included in the sort. B2 contains -19,
whereas B3 is -6399, B4 has -181, B5 has -161, and all subequent cells
in column B appear to be sorted appropriately.

Similarly, when I select Sort Descending, B2 remains -19, where B3 has
8900, B4 has 3272, etc. Again, it appears that Row 2 is not included
in the sort.

Why? If I am doing something wrong, I don't see it (sigh).

When I had this problem before, it was because I did not include a
title row. It was noted that AutoFilter assumes that the first
selected row contains titles.

As "proof" that that is not the case this time, note that when I
select Custom "greater than 0", the cell with -19 (B2) is
appropriately hidden, as expected.

The table was downloaded from a web site. ISNUMBER(B2) is true.