Your recipient may have not opened the message because it came from an unfamiliar number, or they may have opted-out from receiving text messages from American Greetings. You may want to reach out to your recipient and advise them to look for the ecard. If your ecard is not picked up after 30 days, you will receive a notification that your send has been cancelled.
You can also check "My Account" to verify that your ecard appears in "Sent Ecards." If not, then your ecard was not sent. If your ecard is there, then make sure you're connected to the internet and verify your recipient's phone number to ensure that it was sent correctly.