Xerox and FujiXerox are different companies, so we have no access to the device you are referring to, but as a whole, Bypass trays typically cannot be used in Autoselect, so there is no point of setting a priority, so it simply does not allow it to be done. But if it can be made selectable in Autoselect (Consult the user guide) it would then allow a priority to be set afterwards.
No idea what "Check Bypass" could mean, with Xerox it typically tells what to check it for, I guess they don't.
Please be sure to select "Accept Solution" and or select the thumbs up icon to enter Kudos for posts that resolve your issues. Your feedback counts!