I finally got a response just this morning... The Spring sale ended at 23:59:59 on the 28th Zulu time zone. They should have listed that in their advertisement page but did not do so... I am CST. My purchase was at 04:57:59 Zulu on the 29th, which was 23:57:59 CST on the 28th. The cart showed the sale price, but the purchase showed the higher price. That is what prompted the cancellation of the purchase.