Use the correct URL. Instructions for Dropbox here:
Asset hosting through Google Drive may have been deprecated. Perhaps consider using Google Photos as an alternative:
I prefer to use the snippets feature in GitLab. Many use imgur.
I hope this helps.
In Dropbox :
Then you must change the text www. with dl. , So the link like this:
https://dl.dropbox.com/s/yn9fo8iazhe29gu/IMG20190508151239.jpg?dl=0. Then your image Will show.