Continuing the discussion from Issues while updating items:
@ianpkano posted the following on August 30 and never really got an answer as well as getting his thread locked 
So, here is what he really needed to do to get it to work. His original post:
I have completed uploading all items into the item database. but without the supplier info,
I now have the supplier info and created a new file with this, I uploaded a test of 200 items with supplier info and the system ignores the update. I urgently need to update my databases with additional columns of information, but the system will not update.
The answer to his issue:
Well, I think I might have an idea about what went wrong here.
If you used the exact same file that you initially imported and only added the missing columns, then your file did not have enough information to work with in the update.
You see, once you have imported items into the system, you MUST download a new Items template and check the box to include data. This is the file that you must update with the new data columns that were missing before. The file that downloads has additional information that will allow it to properly sync any columns you add to it. More specifically, the file you download now has Column B populated (it was blank when you first imported). This column is what the system uses to match the records and update the information with the new data.
Hope this helps. BKM
I get that @ianpkano vented his frustration, but to be fair, the documentation is confusing on this matter (at least at that time).
I would much rather see the forum actually attempt to answer issues before locking a thread. I just think that was someone being spiteful. So, I answered it anyway.
BKM