Most signup and login forms look identical. They contain a couple of fields, some text, and a button. Their similar appearance can sometimes confuse users into filling out the wrong form.
The user will accidentally fill out the signup form with the intent of logging in or vice versa. After entering their credentials, they soon realize they're on the wrong form. This confusion leads to errors and wasted effort.
You must better differentiate your login and signup to prevent this confusion. Users should be able to identify which form they're on at a glance before they type a single character.
The visual indicator that users have is the page title. However, many will overlook that and focus on the fields first. Therefore, it's necessary to make your page title bigger and bolder. But even then, the text is easy to miss.