Please follow the steps below to add your LinkedIn accounts:
1. Go to FS Poster > Accounts > LinkedIn menu;
2. Click the ADD AN ACCOUNT button;
3. And click the GET ACCESS button and authorize your LinkedIn account.
The LinkedIn token expires when you change your account password or after 60 days of adding your account to the plugin because Linkedin token lifetime is only 60 days. Please delete and add your account to the plugin again when the token is expired.
If your post images are not visible after you share your posts, you can debug your website on the LinkedIn developer page to see the reason.