How to fix Login button does not popup

Ideally, there is another module, js script catch event Click on Login button. So, we should disable them like above comment.

How to fix

Solution #1: 

Open file: app/design/frontend/Smartwave/porto/Smartwave_Porto/layout/default.xml

Remove:

<block class="Magento\Customer\Block\Form\Login" name="header_customer_form_login" template="Smartwave_Porto::html/login.phtml"/>

Solution 2:

Open file: /view/frontend/layout/default.xml

Add the following block XML in body tag

<!-- Fix Popup login -->
<referenceBlock name="header_customer_form_login" remove="true"/>

 See this file