If you get the error above it means your client is not updated.
In order to fix it, you should run your launcher. It should auto update.
If it does not auto-update, you should try the manual patch.
Manual patches are posted at the bottom of the patch notes of each update. The latest manual patch has all of the previous patches in it. Therefore you only need to download the latest manual patch, not all previous ones.
To find the latest manual patch, go to the updates forum which is here: http://dekaronrising.com/index.php?/forum/78-updates-patch-notes/
Open the topic that is the LATEST and download the manual patch inside of it. Then extract it to your game folder.