Hi @Austin G, just so you know, the answer above from @outroRenan solved the problem. He posted it in portuguese, so I will try to translate it for you and the other users with the same problem I had.
It happens that the white window showing up again and again indicates that you have more devices using Evernote than you should. In my case, I use a free account, so I could have only two devices. The (very simple) solution is to go to Evernote web and disable the extra devices.
It worked for me like a charm.
Good luck for you all.
PS: I am not an english speaker, so if my text is no clear, please, fill free to ask me about anything that you couldn't understand.