Error in test mode transaction

I have a problem in setting up Authorized.net sandbox account as a Payment type. I have provided all the credentials. But I still get the following error.
"(TESTMODE) The merchant login ID or password is invalid or the account is inactive. (13)".
I have given the valid login ID and transaction key. I’m stuck here for a week now. Please help me.

This information is provided by the Authorized.net team. We have informed them also about the error. Our sandbox account in authorized.net is in active status.

CODE: 13
EXPLANATION: The merchant login ID or password is invalid or the account is inactive.
INTEGRATION SUGGESTIONS: This error indicates you are either posting the incorrect API Login ID within your script, connecting to a server that does not recognize your account, or using an account which is inactive. Please follow these steps to ensure that your software is connecting correctly:

  • If you are posting your transaction requests to the gateway URLs https://test.authorize.net/gateway/transact.dll and you are using an account given to you by an Authorize.Net Reseller or from Authorize.Net Sales, you may encounter this error. The gateway URLs mentioned above only work with specific test accounts, available upon request by completing the form at https://developer.authorize.net/hello_world/sandbox/
  • Please check your script and verify you are posting the API Login ID for the account in question. If you are not posting the correct API Login ID, or if you are not sending an API Login ID, please edit the script and confirm that the field name is set to the API Login ID that you may obtain from the Authorize.Net Merchant Interface. Please see the Getting Started Guide at https://www.authorize.net/content/dam/authorize/documents/gettingstarted.pdf for instructions on obtaining the API Login ID. For further information on the API Login ID, Transaction Key, or Test Mode, please check out our online video tutorials at https://www.authorize.net/videos/.
  • If you are unable to log into your Authorize.Net Merchant Interface, this could indicate that your account is inactive. Please contact Merchant Support for assistance.
  • If the account is active and the API Login ID is correct, please use the Data Validation Tool to validate the fields you are passing to us.

The most common error with setting up Auth.net accounts is using your actual log-in ID, instead of the API login ID. You cannot use the ID you use to log-in to auth.net. You must go into auth.net and generate the API Login ID. I don’t have one that I can access ATM or I’d do a quick video for you, although the one here is better than I would have done: https://www.authorize.net/videos/

Another consideration, if you’re using a sandbox auth.net account, that may be the cause of the problem. I’ve integrated a bunch of auth.net accounts into Infusionsoft over the years, but have never done a sandbox account. It is my bet that they function differently or may have different perameters that may not function with Infusionsoft which is setup to run to live accounts. Typically, a sandbox account would be used by a developer wanting to setup a new integration, which isn’t necessary with Infusionsoft.