I have scowered google and every resource I can get my hands on, but I cannot get zencart's authorize.net aim module to work. I get the famous error message:

(TESTMODE) The merchant login ID or password is invalid or the account is inactive. - Your credit card could not be authorized for this reason. Please correct the information and try again or contact us for further assistance.

My setup:
1) Hostgator as host
2) sandbox.authorize.net account in test mode.
3) zencart (v1.3.9h) in test mode.


Thus far I have:

1) Guaranteed that my api login id and transaction id are correct.

2) Verified that the http and https servers are correct in config files.

3) Guaranteed that curl is up and running (hostgator set up to use curl)

4) I used the sample here sample php code and it worked just fine using the same id and trans id.

5) I tried using the card # 4111111111111111 from sample.php from above.

6) Set the debug logs option on and tried to use the logs, but it doesn't create any in cache for this error (or it's putting them somewhere I can't find them).

Please help. I really need to get this to work, and I'm all out of options.