PTP.ad relies on browser-side activity signals plus server-side validation.
Qualification may fail if required JavaScript is blocked, the tab is backgrounded, the browser aggressively suspends timers, the ad is not visible, or a privacy/security extension blocks required first-party requests.
Do not disable security software blindly. If a specific browser consistently fails while another works, contact support with the browser name/version and the approximate time of the failed view.