Same issue here but I resolved by clearing my data. This method is just a few steps shorter than DL'ing and installing the app again. I have the following - HTC MyTouch Slide (Gingerbread OS, 2.3.4) - Authentication failed error Motorola Xoom - Syncs fine PC Evernote installation - Syncs fine WARNING: This will delete all Evernote data on your device and you will also have to supply your login credentials when accessing the app again. However, this did not remove data from my Evernote account, just the device. Goto Settings --> Applications --> Manage Applications --> "All" tab --> Evernote Click the "Clear Data" button. That's it. no restart or reinstall...for me anyway. The steps will vary depending on what OS you have; it's even easier to get to the necessary screen on the Xoom. All I had to do was supply my creds (glad I remembered them) when accessing the app afterwards. All my notes then appeared following a quick sync and they matched what was on my other two devices. Just remember to copy whatever original notes appear on your problematic device beforehand; I did so by text-copying/pasting to my HTC-supplied Notes app. Good luck!