The payer is rejecting stating that the accident date you have entered is not valid. The rejection also indicates that it is probably not valid because the accident date you supplied is after the date of service on the claim.
How to Fix
The accident date is in the client chart. Go to your client list and find the client. Once you locate the client, click the edit icon to open up the client chart. On the client chart, click the Advanced button. On the right of the advanced information page, update the accident date to a valid date. Remember to save the client.