Almost every time, if you are not able to complete a social campaign, it means you have already completed it directly from the link and not through the button. You will face an error since system has still not counted your like, retweet or comment yet.
If you want to resolve this error, all you need to do is simply undo from outside and try completing the task from within the system. That means, if you have already liked a post, please "unlike" it by going to the post URL and then use the button to complete the task. If you still face the issue, check your twitter settings and make sure you have logged in properly and you are using the correct Twitter profile.
You can use "Reset Password" button given in the login screen to reset password. You will receive instructions if you are the part of ambassador program. Otherwise, it will say "User doesn't exit" which means, there is no user with this email.