Hello, it’s because the button is commented in the HTML, so change:
FROM:
<!--<div class="d-flex">
<div class="d-none d-xxl-flex custom-header-1-extra-links">
<ul class="nav me-3 mt-1 ">
<li class="nav-item">
<a class="nav-link text-color-light text-2 font-weight-semibold" target="_blank" href="https://www.okler.net/open-a-ticket/">Support</a>
</li>
<li class="nav-item">
<a class="nav-link text-color-light text-2 font-weight-semibold" target="_blank" href="https://www.okler.net/previews/porto/docs/">Documentation</a>
</li>
</ul>
<a class="btn btn-primary font-weight-semibold text-3 py-3 border-radius p-relative bottom-1 custom-header-1-btn-1" href="https://themeforest.net/checkout/from_item/4106987?license=regular&support=bundle_6month&ref=Okler" target="_blank"><span class="px-4 d-block ws-nowrap">Buy Now</span></a>
</div>
<button class="btn header-btn-collapse-nav" data-bs-toggle="collapse" data-bs-target=".header-nav-main nav"><i class="fa fa-bars"></i></button>
</div>-->
TO:
<div class="d-flex">
<button class="btn header-btn-collapse-nav" data-bs-toggle="collapse" data-bs-target=".header-nav-main nav"><i class="fa fa-bars"></i></button>
</div>