Hello Mee, thank you for reaching out to us.

1. If you're using the API method:

This error is returned by the function wp_remote_get which uses cURL in the background. The client's server doesn't have time to manage the data from Google's API in 5 seconds (which is the default setting in WordPress).

That limit can be increased using a hook https://wordpress.stackexchange.com/questions/341357/wp-remote-get-curl-error-28-only-on-same-domain. Instead of "15" set it to "100", just in case.

If you get this error because of the WordPress hook extend_http_request_timeout, you need to remove it from your functions.php file and then checkout solutions for the first initial error for curl error 28 - Operation timed out ...

https://www.wpbeginner.com/wp-tutorials/how-to-fix-curl-error-28-connection-timed-out-after-x-milliseconds/

2. If you're using the old method (without Google's API credentials) the timeout limit is set to 25 in file wp-content/plugins/wpdatatables/source/class.wdttools.php on line 198.

This can be overwritten with the hook wpdatatables_curl_get_data. For example:

function filterCURLOptions($data, $ch, $url){
   $new_ch = curl_init();
   $timeout = 1000;
   $agent = 'Mozilla/5.0 (Windows NT 6.2; WOW64; rv:17.0) Gecko/20100101 Firefox/17.0';
        curl_setopt($new_ch, CURLOPT_URL, $url);
        curl_setopt($new_ch, CURLOPT_RETURNTRANSFER, 1);
        curl_setopt($new_ch, CURLOPT_CONNECTTIMEOUT, $timeout);
        curl_setopt($new_ch, CURLOPT_USERAGENT, $agent);
        curl_setopt($new_ch, CURLOPT_REFERER, site_url());
        curl_setopt($new_ch, CURLOPT_FOLLOWLOCATION, true);
        $data = curl_exec($new_ch);
            if (curl_error($new_ch)) {
                $error = curl_error($new_ch);
                curl_close($new_ch);
                throw new Exception($error);
            }
            if (strpos($data, '<title>Moved Temporarily</title>')) {
                throw new Exception(__('wpDataTables was unable to read your Google Spreadsheet, probably it is not published correctly. <br> You can publish it by going to <b>File -> Publish to the web</b> ', 'wpdatatables'));
            }
            $info = curl_getinfo($new_ch);
            curl_close($new_ch);
            if ($info['http_code'] === 404) {
                return NULL;
            }
   
    return $data;
}
add_filter('wpdatatables_curl_get_data','filterCURLOptions', 10, 3);

This needs to go to the functions.php file of your theme or the child theme (depending on what you're using).