Make sure it is the email you use for Ibotta. You may have typed it wrong. Try entering it again. Wait an hour. Some have suggested turning off your phone and restart it, but I don't know why.
When downloaded, the items can be found under Walmart and listed in the first tab.
If you put on the correct email uninstall and reinstall your app go into walmart it's the first categorey it says free thanksgiving. But just like all bonuses and rebates not everyone gets the same so maybe they didn't give it to you.