I'm using Firefox, and get an error when I try to log in. ES works fine in my other browsers/computers

Hi. You are getting error when you try to log in to Eversync? Can you please write your login here. 

Try to reinstall the extension and also log in on everhelper.me/client first. then check authorization in addon.

Try to reinstall the extension and also log in on everhelper.me/client first. then check authorization in addon.