Twitter card player "Unable to render Card preview"


I am new to twitter card.
I want to integrate video in tweets.
After spending whole day into it i am still not getting the desired result.
I have included meta tags in my site main header and tried to validate .
In first attempt is goes green but video is not playing into it because of incorrect url and after putting the correct url, i again try to validate then it gives me “Unable to render Card preview”.
then i revert the changes and again tried then i got the same message “Unable to render Card preview”.
this is my site : https;//

used these meta tags:

	$https_url = base_url('/assets/plugins/cards-player-samples-master/player/');
	$https_url = str_replace('http://','https://',$https_url);
	$player = $https_url."/container.html";
	$image = $https_url."/example.png";
	$file_link = $https_url."/example.mp4";

<meta content='text/html; charset=UTF-8' http-equiv='Content-Type'/>
<meta name="twitter:card" content="player">
<meta name="twitter:site" content="@BloombergTVIn">
<meta name="twitter:title" content="Testing video">
<meta name="twitter:description" content="This is a sample video.">
<meta name="twitter:image:width" content="480">
<meta name="twitter:image:height" content="480">
<meta name="twitter:image" content="<?php echo $image; ?>">
<meta name="twitter:player" content="<?php echo $player; ?>">
<meta name="twitter:player:width" content="480">
<meta name="twitter:player:height" content="480">
<meta name="twitter:player:stream" content="<?php echo $file_link; ?>">
<meta name="twitter:player:stream:content_type" content="video/mp4">

Can you please help me into this and tell what was I doing wrong and how can i resolve this thing.