Make sure the test member’s email isn’t the same as an existing wordpress admin email. Log ins for test members can’t use the same email addresses as wordpress admins.
Check the password field in a test member record in user’s Infusionsoft app. See if a password is saved in the field.
If no password is present, make sure there’s an http post happening after a new member submits a web form or order form, and make sure it correctly has your http post Auth key added. If it’s not, add &auth_key=yourcustomauthkey to the end of any http posts being sent to your wordpress site.
An example of a correct http post with an auth key properly added is:
http://yourdomain.com/?operation=makepass&overwrite=no&adduser=yes&auth_key=yourcustomauthkey