There appear to be 2 key considerations which need to be taken care of before the image will display for the [summary_large_image] twitter card:
1) The image dimensions must conform (at least) to the minimum width (280px) and the minimum height (150px). Any narrower or shorter and the image will not display.
2) A page cannot (it seems) reference an image ...
In my case my image path had an extra forward slash, which worked fine in-browser, but wasn't picked up by Twitter. It was a one character error that was hard to spot.
E.g. check for this:
And change it to this:
In most cases this can simply be Twitter's card cache. It is very slow to update, up to a week.
To force refresh it, see here: https://stackoverflow.com/a/58842765/2873507
Go to https://cards-dev.twitter.com/validator
Type in the URL you want to update, BUT with a change. For example, add ?utm_source=Whatever
Then just reloaded page with whatever ...
Twitter has it's 140 character limit. That's why you're getting this error. It looks like your description is not automatically truncated to 140 characters.
I would suggest using Open Graph Tags, which are automatically picked up by Facebook, Twitter and Google Plus.
<meta property="og:url" content="https://example.com/your-page-url/" />
Your meta description and meta title are written wrong. In order to be valid opengraph you need to use the property attribute not the name attribute. So in order to fix this all you need to do is change header2.php to...
echo "<meta property='og:description' content='$description' />";
echo "<meta property='og:title' content='$title' /&...
The twitter:player value has to be on a secure server, ie https
Twitter's documentation is pretty bad, but they ask for the twitter:player value to be "HTTPS URL to iframe player". I assume this means the URL of a page which plays the video and has no other content surrounding it, so that it can be placed within an iframe (as opposed to the link you give ...
OpenGraph/Twitter meta tags should be used on any page that anybody is likely to send to someone else on social media or in chat apps. This is the tags' purpose - they make the link appear nicer on social media sites and chat apps.
In practice, this means that all your public-facing pages should have these tags if possible.
Pages behind logins
No, if ...
This is likely due to the low quality and square aspect ratio of your twitter image: https://fireflysemantics.github.io/logo/service-parts-help-center/fs-logo-help-center.png
Twitter renders the card when the image is twice as wide as tall or 16:9 ratio. A square image should not be used.
A two color image is not high quality. Most twitter cards contain ...
Unfortunately this won't be able to be done. The twitter:image:width and twitter:image:height meta tags where supported for the Twitter PhotoCard only however that was depreciated on 3rd July 2015. The summary card with large image (which is what you are using) does not support changing the size of the provided image. Based on Twitter documentation the image ...