The model backing the ‘CloudPanelContext’ context has changed since the database was created. Consider using Code First Migrations to update the database (http://go.microsoft.com/fwlink/?LinkId=238269).
This error message is telling you that your database is not up to date and it needs to be updated. With each upgrade of CloudPanel there may be changes to the database that need to be made.
Some times you are unable to login due to this error. This means that you need to access CloudPanel using a browser on the same server that CloudPanel is installed. Open a browser on your CloudPanel server and browse to http://localhost/CloudPanel/admin/settings and it should load if it detects you coming from localhost or already authenticated.