Magento – Custom magento 2 theme not showing up up on content/design/configuration

I have been trying for two day to figure out how I can customize my magento template. Recently I have become stuck on being able to pull up my new magento theme in the backend admin panel. I have followed the the dev docs to the tee, at least I think so, but I still cannot figure out what I am doing wrong.

Here are the files

Registration.php:

<?php
 

\Magento\Framework\Component\ComponentRegistrar::register(
\Magento\Framework\Component\ComponentRegistrar::THEME,
'frontend/shayan/uub',
__DIR__
);

theme.xml:

<!--

    <theme xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Config/etc/theme.xsd">
    <title>Magento uub</title>
    <parent>boxstore/boxstore_default</parent>
    <media>
        <preview_image>media/preview.jpg</preview_image>
    </media>
</theme>

composer.json:

    {
       "name": "shayan/theme-frontend-uub",
    "description": "N/A",
    "require": {
        "php": "~5.5.0|~5.6.0|~7.0.0",
        "magento/theme-frontend-blank": "100.0.*",
        "magento/framework": "100.0.*"
    },
    "type": "magento2-theme",
    "version": "100.0.1",
    "license": [
        "OSL-3.0",
        "AFL-3.0"
    ],
    "autoload": {
        "files": [
            "registration.php"
        ]
    }
   }

I have already tried

php cache:clear php
php bin/magento setup:upgrade
php bin/magento setup:static-content:deploy