Pro Site Upgrade not showing in Affiliate Referrals

I am using Pro Site together with Affiliate plugin, both network activated. A website is created via Gravity Forms and User Registration add-on. Everything is fine when the website is created, I can see in the Affiliate Referrals chart that there's an increment in Sign Up count. However, whenever I upgrade the newly created website to pro successfully, the referrer does not get credit. In Pro Site's affiliate settings, I already put values (see screenshot) but still nothing is credited to the referrer. I am using stripe as payment gateway and it is in test mode. The transaction is recorded on stripe and the webhook shows Success status. What could be the reason why the referrer is not credited with the site upgrade?