eAuthorize 3.5 and my merchant account

Many of the settings like address verification and so forth will have no impact on the eAuthorize plugin.
However, the Transaction Response settings on your account must be set correctly or the plugin will not properly understand the response to the authorization request. This will often manifest itself with a reponse text message that says, “no such result.”
Log into your account from the Authorize.net web page and click on settings.
The Transaction Version should be set to 3.1. Also, the Direct Response Delimiter must be set as follows:
Delimited Response: No
Default Field Separator: ,(comma)
Field Encapsulation Character: <blank>