Come on people, just go to manage extension > Allow run on sites with restrictions.
I have never had an issue, but Firefox focuses way more on privacy than Chrome so keep that in mind, works great.
I am really greatfull for Evernote supporting the Firefox Addon, that's why I love Evernote.
Hopefully they launch a Linux desktop app :)

国内小伙伴登录扩展时无法跳转到国内印象的，试试看火狐浏览器语言设置为中文，然后重启浏览器。还不行的试试7.26.3版本，以及windows语言也设置为中文。