更新Google AMP缓存内容返回404/403/401错误如何解决

尝试了多种方法更新Google缓存中的AMP内容，查阅了全部相关文档仍未成功，过程中有时返回403、401、404错误，始终未达到预期效果。当前运行以下代码时出现404错误，相关代码如下：

ini_set('display_errors', 1);
ini_set('display_startup_errors', 1);
error_reporting(E_ALL);

$dom = 'https://arthurfrank-xyz.cdn.ampproject.org/';
$update = 'update-cache/c/s/arthurfrank.xyz/amp';
$action = '?amp_action=flush';
$ts = '&amp_ts='.time();

$save_dir = rtrim(__DIR__, '/') . '/' . '.well-known/amphtml/';


$new_key_pair = openssl_pkey_new(array(
    "private_key_bits" => 2048,
    "private_key_type" => OPENSSL_KEYTYPE_RSA,
));

openssl_pkey_export($new_key_pair, $private_key_pem);
$details = openssl_pkey_get_details($new_key_pair);
$public_key_pem = $details['key'];
openssl_sign($dom . $update, $signature, $private_key_pem, OPENSSL_ALGO_SHA256);
file_put_contents($save_dir . 'apikey.pub', $public_key_pem);

/*file_put_contents($save_dir . 'private_key.pem', $private_key_pem);
file_put_contents($save_dir . 'signature.dat', $signature);*/

//validate the signature
$r = openssl_verify($dom . $update, $signature, $public_key_pem, "sha256WithRSAEncryption");


$signatures = '&amp_url_signature=' . str_replace(['-----BEGIN PUBLIC KEY-----', '-----END PUBLIC KEY-----'], '',$public_key_pem);
$url = $dom . $update . $action . $ts . ($signatures);
$url  = str_replace(["\r","\n","\t",' '], '', $url );

try {
    $ch = curl_init();
    if ($ch === false) throw new Exception('failed to initialize');
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    $content = curl_exec($ch);
    if ($content === false) throw new Exception(curl_error($ch), curl_errno($ch));
    $httpReturnCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);

} catch(Exception $e) {
    trigger_error(sprintf(
        'Curl failed with error #%d: %s',
        $e->getCode(), $e->getMessage()),
        E_USER_ERROR);

} finally {
    if (is_resource($ch)) curl_close($ch);
}

echo $content;

报错截图：

内容的提问来源于stack exchange，提问作者handrick johnson