We are using Adobe Acrobat Pro DC (# 2021.005.20048). We are using Highlight tool to comment on images and after saving and re-opening the comments are disappering. The highlighter is convering to a pencil drwaing. It's working fine if we use the funtionality on plain text.
Hope you are doing well and sorry for the trouble. As described you want to highlight/comment on the images and the highlight tool is disappearing on the images.
If it is a scanned pdf then you need to do/run a text recognition/image recognition on the page (or you can also choose the entire document). Once you do that it recognizes the individual sentences and then the text cursor appears. For more information please checkout the help page https://helpx.adobe.com/acrobat/using/edit-scanned-pdfs.html
Let us know if you are referring to something else.
Appreciate your time on this Amal. I am able to highlight and comment on images. But after publishing them the highlight is converting as small line and missing comments. Please see the attached image.