@ estherau:

Ok, that explains your problems. Too bad you missed it, but the cost for Prime membership has been down to 50% for the whole July because of the anniversary...

Anyway, I hope you have seen that the email you got has two offers, one for Prime members and one for all others: 

Save 15% on your next order of $20 or more by entering the coupon code below: 080613B15P20

It is 5% less then what you would have gotten as a prime member, but it is at least a 15% discount and it is still valid until August 8th 11:59pm. Perhaps you may try out if this coupon is working for you?