Senior rates
I think the confusion is that there are 3 senior rate codes with varying levels of availability. There is one for AARP (10%) that is available to hotel desk clerks (no code needed) or online (must enter member number.) There is another one that is CRS only (10%) (online no special code) or through 1-800 AND there is a third one (15%) that is only available through CRS (online with special code) or through 1-800. This is used for senior guests who will not accept the 10% discount.
The online codes do change every so often. So it may be that they have decided to change the 15% senior discount rate code. To get it you may have to book through 1-800 unless you can find the new code.
Zil