What Does it Mean?
The URLs do not have Open Graph tags on them.
Open Graph is a standard that provides rich meta data about a page frequently used to created "cards" about a page when a link is shared on social media or messaging platforms. Although the standard was originally created by Facebook (now maintained by the Open Web Foundation), the cards are used by many other platforms, including Twitter, LinkedIn, iMessage, and Slack.
These cards may contain an image, description of the page, a site name, and other data that is much more visually appealing than just a simple link.
Open Graph tags are <meta> tags with the property attribute set to a list of supported types with the prefix "og:". Here's an example of the "title" Open Graph tag:
<meta property=”og:type” content=”website” />
There are four required Open Graph tags: "og:title", "og:type", "og:image" and "og:url". Without all four of these, the Open Graph data is incomplete and a card may not appear when a link to this URL is shared.
Why It's Important
While Open Graph tags do not directly influence organic rankings, they will likely have an impact on the click-through-rate of social shares of this URL. If Open Graph data is incomplete, a card will likely not be shown which may severely lower the number of people clicking the link.
Including all required Open Graph data will help ensure the card is shown which will lead to more referral traffic from this link. The more people share and visit a link, the greater likelihood web sites will link to this URL as well, thus helping to improve organic search rankings.
How To Fix
Look through the URLs and note which required Open Graph tags are missing. Then edit the metadata on these URLs to include the missing tags. Here are some guidelines on the four required tags:
og:title: A title for this page, similar to the normal <title> tag. There's little need to include keywords, but it should be interesting and make people want to click on it.
og:type: The type of content this URL is. For web sites, it's typically: "website", "article", or "blog". See all types here.
og:image: An image to represent this URL on a card. Aim for an aspect ratio of 1.91:1 and a resolution of 1,200px x 627px.
og:url: The canonical URL of this page.