Can’t add link to image

I use to be able to assign a link to each image I uploaded. I believe I was doing this in the media editor as shown in step 4 here https://www.templatemonster.com/help/wordpress-how-to-link-a-post-image-to-a-custom-url.html I haven’t done anything with my webpage in a few months and now this option is gone. Images that use to link to a custom URL in blog posts I previously published no longer do. Is this a theme issue or is something else wrong?

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