I tried the rollback thing and still Amazon plugin’s SAVE button did not work. I disabled my security plugin and still did not work. Guess what? I disabled my Adblocker and viola! It worked. So if the above suggestion did not work for you, pause your adblocker.
Disclaimer: This is just a suggestion as I spent my whole afternoon going back and forth with Amazon plugin and it was really frustrating. I don’t think anything bad will happen if you pause your adblocker:) but do this at your own “risk.” (I guess YT ads popping):)