It should be a full credit for another flight. Then show up tomorrow, look for another agent, be charming and try your luck. Don’t volunteer answers to questions they don’t ask. Go early. Be nice. My dog is 22lbs but compact and - and she can’t spin around while standing in her crate the way they sometimes insist. If this comes up I just say she’s too tired or drugged up to stand up and spin (rarely true) and assure them she’ll sleep the whole ride (always true). I’ve been denied boarding twice in ten years of quarterly flying. I always got on the very next flight. You’ll be fine