The fine print appears below:
*Offer valid on new bookings made between May 31, 2023 and July 31, 2023 on select 2023 departures. Guests will receive a $500 USD per person air credit (up to $1,000 USD per suite) for air reservations booked through Crystal. For air reservations booked outside of Crystal, guests will receive a $500 USD per person credit on their cruise fare. Offer not valid on the December 23, 2023 departure on Crystal Serenity, is subject to availability, can be withdrawn at any time, and may not be combined with specific promotions. Call for details.
The fine prints does state "may not be combined with specific discounts". However, it does not list what those discounts are. It just says to call for details.
Just out of curiosity... what discounts did you get.?