I've followed this blog post to create a setup for my visitors to subscribe from a wordpress website to a newsletter in CiviCRM. CiviCRM setup is working (I have tested via API Explorer, it works as expected). I have installed Contact Form 7 and it's civicrm supporting plugins to a Wordpress (as described in the post).
I've set the plugin with keys (API and Site) that I've tested. I created a form, filled it and it sent a request to my site and returned a 403 error: "POST /civicrm/sites/all/modules/civicrm/extern/rest.php?json=1&entity=FormProcessor&action=create_subscriber HTTP/1.1" 403
The keys are working but I can't check if they're sent correctly. To see what is being sent in the POST request, I've looked to my browser console, but there was no POST request to my civi installation.
I ran out of ideas to check. What can I be missing?