Amazon sign in not recognized when using Firefox

I cannot log in to Amazon.ca using Firefox. When I input my email address to Amazon, it says I look like a new customer so let's set up an account. I am not a new customer and my account on Amazon works fine if I sign in through the Chrome browser. I have tried refreshing Firefox and also tried using Troubleshoot Mode, but the problem with Firefox persists. Is there a fix? Firefox must be blocking some type of data that Amazon requires but even white-listing the website doesn't seem to work.