Handlebars - Expecting 'OPEN_INVERSE_CHAIN', 'INVERSE', 'OPEN_ENDBLOCK', got 'EOF'

Error states:

Expecting (...), got EOF

Where:

1. (...) is what it can possibly expect
2. EOF is End of File

What you are missing is closing {{/each}}:

{{#each list}}
<ul>
    <li>{{@index}}. {{this}}</li>
</ul>
</br>
{{{htmlTag}}} {{#if user.admin}}
<button class="launch">Launch Spacecraft</button> {{else}}
<button class="login"> Log in</button> {{/if}} {{!-- This is a comment --}}
{{/each}} <!-- HERE -->

This is always as a result of not closing either {{each}}, {{if}}, or any other control statements, but it cannot be caused by unclosed html tags like <div>, <p>, or any other html tags.