One cell won't sort properly in one column

On a monthly basis, I gather Excel reports from 6 different individuals, combine them and perform various sorts. Every once in a while, I have a problem trying to figure out why a simple sort will not work. On the attached spreadsheet, all I want to do is sort Column A first, Column B second and Column C third. You will notice that cell C6 is not sorting properly as it should be down in cell C27. I have a feeling this is so simple, but I'm just not seeing it. Can someone help because after I combine several reports, this happens from time to time and it's really confusing me, especially because it's probably so simple. I'm wondering if it is how the original information is entered. I tried formatting all the cells, but I'm still not getting it. Thanks much!

Hi Joebell,

This is coz A6 is not blank. to confirm this use replace function to replace all blanks with 0. A6 will not get replaced. Before using shorting function replace all blanks cell with zeroes, then such issues could be traced easily.

Thereafter is filtered it, and it working properly.

Thanks Kamal ... that's it. Now I see that A6 actually had a space in it, causing it not to be blank. I knew it had to be simple, but I just couldn't see it. You are a huge help! Thanks much!