This is a known issue with the game and the error 2033 is related to the Save part. By default and in some cases, you only need to Reconnect, but if you still have issues, update Flash to latest version and clear the cache and the storage where Firefox is installed. To do this, press CTRL + Shift + Delete while inside Firefox. Check the cache and the data for apps and then restart the browser. After it's restarted, load the game again and try to connect.
Additionally, use the support page to find additional information: https://helpcenter.kixeye.com/hc/en-us/categories/200071936-War-Commander