Bootstrap 4 Nav Pills doesn't respond when entering the second time

I was creting a bootstrap page with nav pills to change between two html forms

        <ul class="nav nav-pills my-5 d-flex justify-content-center" id="pills-tab" role="tablist">
            <li class="nav-item">
                <a class="nav-link active btn-lg" href="#login" id="pills-login-tab" data-toggle="pill" role="tab">Log-in</a>
            </li>
            <span class="mx-3 d-flex align-items-center"><h5><small>or</small></h5></span>
            <li class="nav-item">
                <a class="nav-link btn-lg" href="#register" id="pills-register-tab" data-toggle="pill" role="tab">Register</a>
            </li>
        </ul>

        <div class="tab-content" id="pills-tabContent">
            <!--Log-in-->
            <div class="tab-pane fade show active col-6 mx-auto" id="login" role="tabpanel">

                <form action="login.php" method="post">

                    <input class="d-none" name="action" value="login" viewonly>

                    <!--Email-->
                    <div class="form-group">
                        <label for="email">Email</label>
                        <input class="form-control " type="email" id="email" name="email" value="" required>
                        <div class="invalid-feedback">

                        </div>
                    </div>

                    <!--Password-->
                    <div class="form-group">
                        <label for="password">Password</label>
                        <input class="form-control" type="password" id="password" name="password" required>
                        <div class="invalid-feedback">

                        </div>
                    </div>

                    <!--Submit-->
                    <input class="btn btn-primary" type="submit" id="submit">

                </form>

            </div><!--Log-in-->

            <!--Register-->
            <div class="tab-pane fade" id="register" role="tabpanel">

                <form class=" col-6 mx-auto" action="login.php" method="post">
                    <input class="d-none" name="action" value="register" viewonly>
                    <!--Name-->
                    <div class="form-group" id="name-form">
                        <label for="name">Name</label>
                        <input class="form-control" type="text" id="name" name="name" required>
                        <div class="invalid-feedback">
                        </div>
                    </div>

                    <!--Username-->
                    <div class="form-group" id="username-form">
                        <label for="username">Username</label>
                        <input class="form-control" type="text" id="username" name="username" required>
                        <div class="invalid-feedback">
                        </div>
                    </div>

                    <!--Email-->
                    <div class="form-group" id="email-form">
                        <label for="email">Email </label>
                        <input class="form-control" type="email" id="email" name="email" required>
                        <div class="invalid-feedback">
                        </div>
                    </div>

                    <!--Password-->
                    <div class="form-group" id="password-form">
                        <label for="password">Password</label>
                        <input class="form-control" type="password" id="password" name="password" required>
                        <div class="invalid-feedback">
                        </div>
                    </div>

                    <!--Repeat Password-->
                    <div class="form-group" id="repeat-password-form">
                        <label for="rep-password">Repeat Passwords</label>
                        <input class="form-control" type="password" id="repeat-password" required>
                        <div class="invalid-feedback">
                        </div>
                    </div>

                    <!--Submit-->
                    <input class="btn btn-primary" type="submit" id="submit">

                </form>

            </div><!--Register-->

        </div><!--Pills-->

I noticed that the first time that i visit that page it all works but if I go to the home page (or when I simply refresh) and then back to this page the nav doesnt work anymore.

I also noticed that if I chose the first option (default) and i refresh it works.

I don't really know what to do.

I'm using Node for backend.