Hey. You can try this method. My internet speed was 40MBPS and used LAN (as I tried 3 times over wifi but not able to pay). Use windows the system if possible.
Try this following these steps.
1. Use Microsoft Edge browser.
2. Login at 8:00 MST.
3. Go to Complete Draft Application or Make online Payment
4. Quickly check all the details one by one. (complete within 10 minutes)
5. Go to final payment page (where credit card and preview option is there) Initially, it will show IQAS daily limit of applications for immigration purposes has been reached for today.... . But here is the catch, refresh the page 1 or 2 times (you will get same message of daily reach)
6. Now do final refresh at sharp between 8:14:30 MST (if less than 30 MBPS) or 8:14:40 MST (If 30+ MBPS), once the page refreshed, don't wait, just click preview and payment. Bang!! (Don't wait for preview file).
7. Don't forget to on pop up from the setting (Check Youtube).
8. Finally, another page will open, then you have 5 minutes for final payment.
9. Cheers!!!
I hope this will work for you. All the best....