The share image is too small, or the wrong shape

Networks choose the layout of a link preview from the size of its image. Facebook: "Use images that are at least 1200 x 630 pixels for the best display on high resolution devices. At the minimum, you should use images that are 600 x 315 pixels to display link page posts with larger images", and under 200×200 the image is not used at all. LinkedIn shows anything under 401 pixels wide as a thumbnail. A small image becomes a postage stamp beside the text instead of a card across the feed. Cards are about 1.91:1, so a square or tall image has its top and bottom cropped away.

Sources: Facebook: images in link shares; LinkedIn: make your website shareable.

Export the image at 1200×630 pixels, keep anything important away from the edges, and tell networks its size so the first share doesn't have to wait for a download:

<meta property="og:image" content="https://www.example.com/share.png" />
<meta property="og:image:width" content="1200" />
<meta property="og:image:height" content="630" />