This is exactly what happen to my desktop version account. I already have checked the devices. I think it is not the source of problem. I also tried to login the web version, my account is fine and I am able to login.
However the version 10,xx keeps give me internet connection problem.
FYI I tried it on my personal computer, there's no such thing as firewall setting because currently I use the version 6,xxx desktop version. (Revert back to version 6,xxx is the only option that I have)
I already asked this on the Evernote's Community Facebook Grup, but it seems there's no fix yet. Many people experience the same. I do not know if the Evernote realize this problem and try to address it properly.