In my case, the button was missing because it was a multisite install. The Add New button appears only when you go to the top bar -> My Sites -> Network Admin -> Themes. From there, you can add new themes and enable them for the rest of the network.
Edit config file Go to cpanel -> File Manager -> wp-config.php Click on edit
Scroll to the bottom Change define(‘DISALLOW_FILE_EDIT’, true); define(‘DISALLOW_FILE_MODS’, true);
to define(‘DISALLOW_FILE_EDIT’, false); define(‘DISALLOW_FILE_MODS’, false);
This fixed it for me
Never run through such a problem but I can suggest you do the following:
If you are a Linux user:
$cd path_to_your_wordpress_site/wp-content/ ls -lah $sudo chmod -R 755 themes
Here h flag to ls command will show you all the ownerships and permissions related to the file. If it didn’t help either
go to the root directory of the webserver:
sudo chown -R www-data:www-data your_wordpress_site_folder
above command is for ubuntu
$sudo chown -R apache:apache your_wordpress_site_folder
Themes are just sub-folders in
wp-content/themes, when you upload a theme in a zip file to the themes page, it just unzips the file into that folder. If it’s a valid theme then it shows up on that page.
If for whatever reason this functionality is disabled, or write access isn’t possible, that option won’t present itself in the user interface, but I would recommend using the manual process instead