If your account is new, make sure you have activated it with the email sent on registration.
Also check if you are able to login to the Trailforks website. https://www.trailforks.com/login/
If you are still unable to login to the app, you might have some bad cached user data, you can use a hidden debug option in the app to force a logout which clears all the user data.
To enter debug mode in the app, tap the small Trailforks logo on the menu 5 times, this will reveal debug options. Goto the "Payload Test" option then choose "logout".