If you are trying to log in and TapChamps tells you that the email you're trying to use is already in use, it means that you must have already created an account with it in the past.
To fix this issue you can:
1- Add a different email address to the account you're currently using.
2- Log into the previous account you created and change the email used there under the Profile Page in it.
3- In case you didn’t create an account using this email, and believe your email has been used without your consent, please send an email to firstname.lastname@example.org, sharing the email in question and we will start our investigation.