We show the generic thank-you page stating "The Payment processor has not yet informed us about your payment" whenever a buyer arrives at that page before we have received payment confirmation from the payment processor (e.g. PayPal). This can happen if it takes the payment processor significantly longer to complete the payment than it takes the buyer to finish checkout.
Once the buyer proceeds from checkout to their thank-you page, if we haven't already received payment confirmation by then, we stall the buyer for up to 60 seconds (in 10 second increments at a time) to allow more time for the payment confirmation to come through; if payment still isn't confirmed after 60 seconds of waiting, we would show the generic thank-you page. Once we finally get payment confirmation and process the order, we would send the buyer thank-you email(s) providing a link to their thank-you/download page.
If you're seeing the affected orders in your E-junkie Transaction Log, that would confirm we are processing those orders as soon as PayPal sends us IPN confirming they've completed the buyer's payment, so the problem may be that PayPal is taking longer to process payments for mobile users lately for some reason.
You can confirm if this is the case by comparing the "Payment Date" (when the buyer finished checkout) vs. the "Processed by E-j" (when we received IPN from PayPal) timestamps for affected orders in your Transaction Log; if these are more than 1 minute apart, that would indicate PayPal took too long to complete the payment, so we had to show that buyer our generic thank-you page after checkout.
If you are not selling digital goods, you can disable waiting for payment confirmation by un-checking "Wait for pending payments..." in your Seller Admin > Payment Preferences screen. In this case, we would process your orders and allow buyers to access the proper thank-you page for their order as soon as they finish checkout, without waiting for final payment confirmation first. We DO NOT recommend this for sellers with digital goods, as some payments could ultimately fail after the buyer has already obtained their digital item (file download, purchased code, etc.).