If you have linked Ibotta with Target, then Target may not be listed under Redeem. If you have your accounts linked, you don't need to submit your receipt. It should happen automatically, but it could take a day or more.
The easiest way to find Target is to do a search on the Home page. Just type in Target.
If this still doesn't work, I would try resetting your phone, clearing cache and even checking for a new update from Ibotta.