Try going to Ibotta.com and sign in there. If you enter the correct email address and password, it should ask you how to verify you. Either select the email address or the phone number.
If you are not getting to this screen, then you are not entering in the email address you signed up with in Ibotta or the password is not correct. I know it may seem silly, but make sure you don't have caps lock on.
I just tried and it worked fine for me.