Instacart complaint: Unusable Coupons False Advertising

I had received an advertisement on my main Instacart screen that I had $40 off of an order of $80 or more. When I went to use it I had to use a code, one I had never been given. I contacted customer service and was informed to look for an email later that day. Three days later, the offer was about to expire, and still no email had arrived. I was waiting and purposely looking for it, checking SPAM folders and all. I contacted customer service again and after quite a bit of time was finally told that the coupon offer was no longer available. I would like to know three things:
1) Why did I never receive promised email?
2) If promotion was not available why was it still on my screen, taken up so much space that it was difficult to navigate the app?
3) Why is something being promotedoffered that they will not see to completion?