I'm having trouble getting a basic transaction to work. Everything seems fine, until you click "Pay Now", and then it comes back with this message:

Error: There was a problem processing the payment: The merchant login ID or password is invalid or the account is inactive.

Here is my setup:

• Drupal 6
• MS Membership Suite 6.17
• Authorize.net developer acc't
• test mode.
• MS Membership license keys are entered.
• Authorize.net API Login ID / Transaction Key entered.
• AIM transaction mode: Developer test account transactions
• ARB & CIM both set to 'disabled'.
• MD5 hash entered (a string that I made up and entered both in the ms/auth.net config, and in the auth.net account).
• I have even turned off "Password-Required Mode" in the auth.net UI, hoping that might help.

Any ideas? I'm not even sure what the "merchant login ID or password" is, as there are no fields anywhere for me to enter that info into the moneyscripts UI. I've tried resetting the transaction key a zillion times, have flushed the cache, upgraded to the latest version of moneyscripts, and I'm still stuck on this one error message.

Thanks!

Dan
(working on behalf of Aaron, whose MS acc't this is).