Can't Log In on Firefox

I've been having trouble loging into Polygon via Firefox and Firefox mobile. This trouble started about a week ago. I was automatically logged off of my account on all my devices (PC, phone, and tablet). When I attempt to log back in, everything seems to work as normal, but when the page refreshes I am still not logged in. I tried disabling all plug-ins and running in safe mode, but that did not fix the issue.

I am running Firefox 48.0.2 on my PC at work, 50.0.1 on my PC at home, and Firefox Mobile 50.0.1 on my tablet and phone. Chrome and IE still work correctly.

Any help would be appreciated.