Originally Posted by Points Scrounger
I would call Rewards Network to see whether they can add it at their end. If not, I'd call the credit card company and explain the situation to them.
Diners Club (since before the MC conversion and also since) has been automatically linked to the Restaurant Savings Program, which is administered by iDine/Rewards Network. (It's a 20% cashback, "free" with the card, tho the card is far from free.)
Because the card is automatically tied to that program and cannot be removed from it, it cannot be used for any other iDine program.
(This MAY also be the case with the credit cards officially associated with airline programs, such as Citibank's AAdvantage MC, which are typically automatically associated with that airline's iDine program, but in that case they have the ability to align it with a different AA FF account -- in case they assign it to the wrong one first -- so I'm not sure there.)