Problems with highlighting

Hello! I'm having a problem with the highlight tool. When I select a text to highlight, the tool highlight it but only around the text (example on the image), not over the text as it used to in my old notebook. I have visual problems so it is difficult for me to differentiate between a highlighted or not highlighted text 😞

I've tried changing prefferences, different  documents where I knew I was able to highlight before and closing and restarting Adobe Acrobat Reader but my problem remains.