How to fix the problem: cannot find or install theme in Dashboard in WordPress

Reason : permission not allowed

Method:

Step 1:  chown -R www:www your-wordpress-dir  because default user group of nignx is www  ( /usr/local/php/etc/php-fpm.conf point to default user and user group)

Step 2: (key) : remove scandir function indisable_functions of /usr/local/php/etc/php.ini

Step 3: restart server, if you use lnmp, like this ./lnmp restart