Hi Fienyx,
Try the following settings.
Form action: https://bizassure.infusionsoft.com/app/form/process/0816d21e38fd550fc957f58b670e3b0d
Email identifier: inf_field_Email
Name identifier: inf_field_FirstName
Additional name / value pairs (name : value):
inf_form_xid : 0816d21e38fd550fc957f58b670e3b0d
inf_form_name : BizAssure Blog
infusionsoft_version : 1.23.8.42
That should do it. You can try leaving off the infusionsoft_version field, but I'm pretty sure you can't leave the form_xid and the form_name. Let me know how this worked for you!
O, and please vote 'works' if the current plugin version works fine for you with the latest WordPress version. http://wordpress.org/extend/plugins/newsletter-sign-up/