Why did the lead not get to the service if the send only after payment option was not selected?

The checkbox for sending data only after payment is available in several sections of the website settings. This rule can be set at the payment system level and at the individual receiver level. 

By default, the connected payment system settings include a rule that prohibits sending orders to data capture services without payment. It is available at the bottom of the page with payment integration settings and looks like this: