If you see this error on Facebook, it just means no list has been chosen for your Page just yet.
- In your MailChimp account, go to Account > Integrations.
- Click Facebook to open the Facebook integration details.
- In the configure page drop down menu, choose the Page you want to configure.
- In the list to use drop down menu, choose which list's form you want on this page. If you don't want a form on this page, just choose no list connected.
- Click the yes radio button for use signup form tab to activate the tab on the page. This will open additional options for the form.
- In the form theme drop down, choose which form style you'd like. If you choose My List's Theme (default), your signup form will look like your MailChimp hosted signup form. If you select Facebook-esque, your signup form will blend more into Facebook's overall look.
- Assign a name for your tab. This is what will show on your Facebook page for visitors to click to access the signup form.
- Click save and wait for confirmation that your changes have been saved!
- Choose another Page from the Configure Page drop down menu to select the options for that Page. Remember to click save for each Page you edit.
Facebook removed the ability to add Application Tabs on profiles in November, 2010, so signup forms can only be added to Pages.