Btw; also tested this with the help of Automattic.

I'm guessing you mean login credentials, if so, I cannot reproduce. I can logout and login without problems.

Maybe clearing your local config will help rm -r ~/.config/Simplenote

Yes, I mean login credentials. Tested it _again_. Deleted the app I downloaded from simplenote.com, deleted the Simplenote folder and restarted the computer. Installed from Software center, and still the same error (https://i.imgur.com/qE94sRI.png).

Rune

On first glance that looks like a wrong password :P If the tarball from simplenote works fine, please double check stuff like your keyboard layout and if you have weird symbols in your password consider changing it.

I can confirm this here, I can login with the same email/pass from chrome or firefox fine but with the simple note app from the repo it just refuses to login

password is very simple, there are no odd or special characters