I just SOLVED it for myself!!
What needs to happen is this.
1) Create a thumbnail and add the code to your ‘excerpt’ section as done in the past
2) Post your new blog-post so that it is assigned a permalink id. eg: https://www.something.com/?p=24
3) Go back to ‘edit’ your post and in the ‘excerpt’ field. You will see that after <a href=”…. comes a link to an image. You need to replace that with a the permalink to your post! It will then read like: <a href=”https://www.something….
4) Click update and it’s done and working!!
Post the code for the thumnail as usual in the ‘excerpt’ section.