Anyone know how to fix a brand new fresh install of Magento 2.1 when instantly upon installing NONE of the panels are expanding in Admin System Configuration?? Kinda hard to setup a store when a fresh new install has an immediate problem that doesn't even allow setup.
run this command i think its working for you
php bin/magento setup:static-content:deploy
php bin/magento cache:flush
php bin/magento indexer:reindex
php bin/magento setup:upgrade
When not in production mode Magento 2 will try to create symlinks for some static resources. You can change that behavior by doing the following.
Open app/etc/di.xml and find the virtualType name="developerMaterialization" section. In that section you'll find an item name="view_preprocessed" . You can modify it by changing the contents from Magento\Framework\App\View\Asset\MaterializationStrategy\Symlink to Magento\Framework\App\View\Asset\MaterializationStrategy\Copy
after that Delete the files under pub/static to get read of any existing symlinks. You may want to be careful not to delete the .htaccess file.
The following is taken from https://magento.stackexchange.com/a/64808/594