how to perform an item massive update via spreadsheet from manage items

Summary:

Hello,

I'm not able to perform a Massive Item Update from spreadsheet.
Our clients need to do it by themselves but seems to be not possible.
I tried and made some tests, when I download the Excel file and I update some fields, then from Add-Ins I Validate my spreadsheet, then I generate a Token and then I upload my file in Oracle.
There is a process that runs at this moment, the "Item Import" one and it succeded.
Then, I come back to see the modifications on items but they are not updated.

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