I'd talk to cakewalk directly. The only way to
upgrade to X1 production Suite was via the Cakewalk Store. in this store, for this very item "Sonar X1 Production Suite
(Upgrade)", it was stated that this offer for this very item is valid until the end of october.
They can't make an offer, and the delete it from the store, claiming that the offer is still valid, but not for the upgrade, but only for the full version, or, the offer for the upgrade is still valid, but there won't be anyone to buy it from.
clearly an unfortunate mistake by cakewalk, but it was THEIR mistake, not yours, and they should show responsibility for their actions, no matter how generous they were before, or are now, with all their other promotions.
Contact Cakewalk. This was a bloody good deal, getting X1 Production Suite, the PC4k Gate/Expander, Z3ta+2, X2 Producer and the DSF Symphonic Strings for only 80€ when upgrading to X1 Production Suite, the offer for it - the
upgrade - valid until the end of october. It was Cakewalks offer, I accepted, and Cakewalk can't put that offer down when they announced it valid until the end of october.
THEIR fault, not your's. The misleading seems obvious to me, you deserve an excuse at least, no more explanations.
There even WON'T BE any more explanations, along with no excuse, as Andrew said his last post will be his last reply on this topic, so I definately would contact Cakewalk directly.
Good luck.