Get this error after installing Opt-In Plug-In in Wordpress... Couldn't resolve host '.infusionsoft.com'

CURL error: Couldn’t resolve host ‘.infusionsoft.com’

I followed all instructions for installing Infusionsoft Opt-In plug-in on my wordpress site, but when I test it i get this error.

CURL error: Couldn’t resolve host ‘.infusionsoft.com’

Any ideas on how to solve? In other opt-in integrations I always had to create a campaign and integrate the opt-in with a specific campaign.

It appears the subdomain is not set. This will be your application name.