Highlight symbol is gone after each sentence is marked

Hey there!

* Maybe I'm posting this in the wrong category so please forward this to the right one if needed.

So I have some PDF files I'd like to highlight some things in them. I have done this a thousand times before - on other files and also I've done this to some part of the current file I'm trying to work on.

The problem is that every single time I highlight a sentence, the highlight marker is gone and I need to click on the "highlight" symbol each time before I want to highlight any sentence and it's really frustrating.

This is the very first time it occurs to me and I don't know what's wrong. I closed and re-opened the file a couple of times and nothing helps. It also seems to happen on any other PDF file on my computer. I checked the same files on another computer and there is no problem at all so the problem might be with the settings on my computer.

Your experience and help are requested please 🙂

Thanks in advance