Mouse pointer works but mouse has no effect in LibreOffice

Hello quality rescuers!

First of all, I'm sorry if I'm not in the right place; I wasn't sure if I should post this in "mouse" or "Libre Office," since it concerns both. Please feel free to move it if you think my request would get more responses in another thread.

So, here’s the thing: something strange is happening: since yesterday, my mouse is unresponsive, but only in Libre Office. It works for general commands: going on Google, choosing a site, browsing the site, writing a message, and then selecting text to delete or correct it, for instance. I can also move the window of the site being visited. Etc.

But in Libre Office, I can't do any of that: only the pointer is active: I can certainly move it around as I want, but the action I want to perform, whether in the text or in the menus, does not happen. For example, I can position myself in a text to select a word or a passage, but the selection doesn’t occur, or it starts to happen, then stops... To close a document, I can position myself on the little red cross, but nothing happens. I'm forced to juggle with the touchpad, which I hate because it's totally crazy (always has been). I can't move my document (open) on the screen, nor use the scrollbar. Etc.

Before reaching out to you, I checked a few answers because I like to try to solve things myself. I had hope with a simple manipulation: removing the USB thing from the mouse, pressing both the left and right clicks simultaneously, and while holding that down, putting the USB thing back: it worked for 2 minutes, then the problem returned. I also changed the battery (even though I was sure it wasn’t that).

I read here some cleaning tips using a thing whose name I forgot, but anyway, my mouse is about ten years old, and I don’t have a manufacturer's name. When I go to properties, I see Microsoft as the Manufacturer. I went into the mouse settings and did "troubleshoot," but the verdict is that no problems are detected (which I can understand since the issues only arise in Libre Office).

Do you have any ideas? If so, thank you because I’m at the point of considering buying a new mouse (I see they’re around 20 euros).

THANK YOU!!!

Whovi, former Whovian, who has to regularly change her username because she’s not recognized (GRR!!!)