Hi, just because extensions are recommended, it does not mean that they won't break something on certain sites. So to find out if one of them is causing your problem, hold down the Shift key when you start Firefox to start in Safe Mode. More - Diagnose Firefox issues using Troubleshoot Mode.

If it's OK in Safe Mode, disable any theme and your extensions - 3-bar menu > Add-ons > Themes/Extensions, then restart Firefox; now if it's still OK, re-enable them one by one until you find the culprit. You may need to restart Firefox after enabling some extensions.

If your question is resolved by this or another answer, please help other users by marking the best reply as Solved. Thank you!

OK, the next time I have to make a payment, I will do this ... in the meantime I used chrome so that I could make my purchase immediately! I will come back to confirm if it worked or not as soon as possible. Thanks for the explanation.

Which extensions did you install ?

Are that extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) that can block content (e.g. Adblock Plus, NoScript, DuckDuckGo PE, Disconnect, Ghostery, Privacy Badger, uBlock Origin) ?

• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

Firefox shows a purple shield instead of a gray shield at the left end of the location/address bar in case Enhanced Tracking Protection is blocking content. You can click shield icon for more detail and possibly disable the protection. You can check the Web Console for messages about blocked content.

• https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop
• https://support.mozilla.org/en-US/kb/trackers-and-scripts-firefox-blocks-enhanced-track

i've install "Privacy Badger" but i remove, and restart FireFox without probant result. The shield is alway gray, and no tracker detected.