Originally Posted by retiredfromhilton

Diamond and Gold upgrades are on a 'space-available' basis. Simply because a rooms or suites appear to be empty on Hilton's app does not mean they are available for complimentary upgrade. They may be being held for hoped-for last minute arrivals. Or the hotel may simply wish not to make certain room or suites types eligible for complimentary upgrade or to make those rooms available only as case-by case basis. If a property chooses not to make certain suites available for complimentary upgrades, then they are, by definition, unavailable.