PHP：简单的HTML DOM。 无法获取网站HTML

I'm new using the Simple HTML DOM Parser class, and although I have been investigating about it, I don't know the cause of my error.

I have tried with 3 diferent methods, that I have used before and worked. I would like to get the HTML of this webpage: Central Bank of Bolivia.

I have first tried with this:

$html = SHD::file_get_html('https://www.bcb.gob.bo/');

Then with:

$url = 'https://www.bcb.gob.bo/';
$html = null;
while ($html == null) {
$html = SHD::file_get_html($url);
}

And finally:

$url = 'http://www.bcb.gob.bo/';
$timeout = 30;
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_USERAGENT, $_SERVER["HTTP_USER_AGENT"]);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, $timeout);
curl_setopt($ch, CURLOPT_FAILONERROR, 1);
$contents = curl_exec($ch);
curl_close($ch);
$html = SHD::str_get_html($contents);

The first and the second attempts, they both throw a certificate error. The last one, just returns nothing, a blank page. This is weird to me because they worked when I wanted to get another webpages' HTML.

I would appreciate any help or answer to why is this not working. Sorry if the question is bad-edited, I'm new here.