Referral not working

I am testing this plugin, looks great.

I am not being able to create a referral. I got the link, I am accessing in a “private mode” window, it register the visit and click, so all good. But I’ve configured to create a referral on user registration (users on the webiste that I am building will pay a subscription on their registration – using Formidable Forms and Stripe to register the user in WordPress), but the referral is not being registered at all.

Some guidelines to follow?