Authorize net Error Code 99

We had our shopping cart working tolerably for quite a while. Someone changed the Transaction key on Authorize.net to try to integrate another program. They did not make a record of the new transaction key. I went and generated yet another one and entered it into the gateways.php file, pushing my changes to the remote server. We are still receiving the error code 99. Authorize.net has a troubleshooter for the 99 code but I feel like the issue has to be related to the transaction key which is one of the details asked for by the troubleshooter. The only details asked for by the troubleshooter that I know how to find are the transaction key, login ID and price of the item being purchased. I need help getting this error cleared so we can resume ecommerce traffic.