If you experience the error code F7121-128 while trying to watch Netflix on your Firefox browser, it typically points to an extension not allowing Netflix to work properly. Follow the troubleshooting steps below to resolve the issue. Disable Extensions Open Firefox if it's not yet open. Select the Firefox menu icon (which can vary depending on the version of Firefox you're using). Select Add-ons. Select Extensions. Select Disable on the shop@home add-on. Try Netflix again.
