How To Enable Online Pre-bidding
For Silent Items auction pre-bidding the Allow online pre-bidding option must be checked on the silent item (and should be, by default, for new silent items).
If you need to turn this on, or off, en-masse you can do so efficiently from the item list report.
Open the item list report.
Click on the report menu and choose Open View.
Click on the Pre-bidding for silent auction view.