Don't know what entity you are dealing with, but I would expect that there is a review option available. Should be in the fine print of whatever they gave you. Try Google with the name of the organisation and something like review rating or decision.
You may need additional backup for the review, so see if you can get a specialist to do a report.
Sometimes I think they give the first attempt a low score to weed out the weaker cases. if you persist, with the right backup, you might do well. but you must be well armed with solid medical evidence.