Payment workflow "Payment success" not triggering!

Payment workflow "Payment success" not triggering!

Hi guys,
I just released an application yesterday using Creator for people to sign up and pay for dance classes. The form is embedded on a website. When they submit the form, they're redirected to paypal, since we're using a payment workflow. In "payment success" of that workflow, which is linked to the form, I set the current record to "Paid = 'Yes'" and create an invoice on Zoho Invoice. I was never able to test it because there isn't any Paypal sandbox on the new version of Creator. Today I've been receiving payments from Paypal from our first customers, with the right amount and everything, but nothing is getting updated! All the customers have Paid = 'No' and no invoices or contacts have been created! Why is that happening?