MailChimp Error: API Key cannot be blank I'm trying to install the mailchimp addon but are stuck on getting the error message above.

So far:


I've installed/enabled the module with version 7.x-4.0
Loaded the PHP Library to /sites/all/libraries/mailchimp
Added the API Key to /admin/config/services/mailchimp
Enabled the MailChimp Signup module


The error occurs after enabling the signup module and freezes the whole website with a blank screen even though error messages are being fully displayed. When I uninstall the signup module via drush and check the admin page for the service my API key is still set.

Any pointers what I'm doing wrong?
Mistake: I've not correctly installed the mailchimp php library. Instead of showing this in the status report page the module crashes the website.