Button Gradient and Social Button is Not Working

<section class="form-elegant sign-up">

<div class="container ">

<div class="row d-flex justify-content-center">

<div class="col-md-6">

<!--Form without header-->

<div class="card">

<div class="card-body mx-4">

<!--Header-->

<div class="text-center">

<h3 class="dark-grey-text mb-5">

<strong>Create an account</strong>

</h3>

</div>

<!--Body-->

<div class="md-form">

<i class="fa fa-user prefix"></i>

<input type="text"id="inputIconEx2"class="form-control"mdbInputDirective>

<label for="inputIconEx2">Full Name</label>

</div>

<!-- Material input -->

<div class="md-form">

<i class="fa fa-envelope prefix"></i>

<input type="text"id="inputIconEx1"class="form-control"mdbInputDirective>

<label for="inputIconEx1">E-mail address</label>

</div>

<!-- Material input -->

<div class="md-form">

<i class="fa fa-lock prefix"></i>

<input type="password"id="inputValidationEx2"class="form-control validate"mdbInputDirective>

<label for="inputValidationEx2"data-error="wrong"data-success="right">Type your password</label>

</div>

<div class="text-center mb-3">

<button class="btn btn-block purple-gradient btn-rounded waves-light "mdbWavesEffect>Purple</button>

</div>

<p class="font-small dark-grey-text text-right d-flex justify-content-center mb-3 pt-2"> or Sign in with:</p>

<div class="row my-3 d-flex justify-content-center">

<!--Facebook-->

<button type="button"class="btn btn-fb waves-effect waves-light"mdbWavesEffect>

<i class="fa fa-facebook white-text text-center">

</i> Facebook</button>

<!--Google +-->

<button type="button"class="btn btn-gplus waves-effect waves-light"mdbWavesEffect>

<i class="fa fa-google-plus white-text"></i> Google+</button>

</div>

</div>

<!--Footer-->

<div class="modal-footer mx-5 pt-3 mb-1">

<p class="font-small grey-text d-flex justify-content-end">Already have an account?

<a routerLink="/login"routerLinkActive="active"class="blue-text ml-1">Sing In</a>

</p>

</div>

</div>

<!--/Form without header-->

</div>

</div>

</div>

</section>