This worked for me trying to upgrade an older version of WP on an old server, by adding below code in functions.php of the theme folder:
add_action(‘http_request_args’, ‘jkudish_http_request_args’, 10, 2);
function jkudish_http_request_args($args, $url) {
$args[‘sslverify’] = false;
return $args;
};