I deleted the coupon a prize copies its rules from

That prize cannot be won until you act, like a sold-out prize. The Wheel screen and the Dashboard name it straight away, and the line under the prize says the coupon is not published. Choose other coupon rules, remove the chosen coupon to use the Coupon Defaults on purpose, or restore the coupon from the bin (or publish it again, if it was set to draft or private). Saving the wheel without doing one of those leaves the prize out. If it was the only prize that could be won, the wheel stops showing on your shop until you do, and the Dashboard says No prize can be won right now.