Found the answer via heather in response to “Switch back to silverlight from flash player?”
Go to this link.
https://www.amazon.com/gp/video/settings?ie=UTF8&ref_=aiv_rdr_pin
Scroll down and you will see where the amazon player preferences are located. It’s not easy to find. I had to contact Amazon support via chat. They are super friendly and helpful tho!
Look for something that looks like this::
Allegedly you can experience less buffering and enjoy HD titles with Microsoft Silverlight on your Amazon Instant Video streaming. According to Player Preferences, your setting applies to Firefox, Internet Explorer and Safari. Silverlight is no longer supported by Chrome.