I can't find modal in Your code. Please verify it with our documentation page:
https://mdbootstrap.com/docs/vue/modals/basic/

Best regards

<template>
<div>
<section class="form-elegant" v-if="!loader">
<mdb-card>
<mdb-card-body class="mx-4">
<div class="text-center">
<h3 class="dark-grey-text mb-5"><strong>Adicionar tipos de notificação</strong></h3>
</div>
<mdb-input label="Your email" type="email"/>
<mdb-input label="Your password" type="password" containerClass="mb-0"/>
<p class="font-small blue-text d-flex justify-content-end pb-3">Forgot <a href="#" class="blue-text ml-1"> Password?</a></p>
<div class="text-center mb-3">
<mdb-btn type="button" gradient="blue" rounded class="btn-block z-depth-1a">Sign in</mdb-btn>
</div>
</mdb-card-body>
<mdb-modal-footer class="mx-5 pt-3 mb-1">
<p class="font-small grey-text d-flex justify-content-end">Formulário destinado a inserir novos tipos de notificação</p>
</mdb-modal-footer>
</mdb-card>
</section>
<div v-else class="row">
<div class="col-md-12 text-center">
<loader></loader>
</div>
</div>
</div>
</template>
<script>

Hi there,

Could You please share Your code with us? It would be much easier to cooperate and fix that issue.

Best Regards