You had to have used the Premium edition of TurboTax Online to be able to add business related expenses. If you used the online version, and originally only paid for the Deluxe version, you won't be able to add expenses unless you switch to the desktop software.
You can add business expenses to any version of the desktop program, but you needed Premium to do it in TurboTax Online.
TurboTax Desktop - Amend
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