Hello DennGuez,
Welcome to Apple Support Communities!
We want to help ensure your mouse and macOS as working properly together.
As this sounds like a software retailed issue, let's make sure you have all pending updates installed.
This can help make sure macOS is working as expected. Use these steps to check for updates: Update macOS on Mac - Apple Support
"Use Software Update
Before installing new software, it's a good idea to back up your Mac.
- From the Apple menu in the corner of your screen:
- Choose System Settings. Then click General in the sidebar, and Software Update on the right.
- Or choose System Preferences. Then click Software Update.
2. If Software Update finds new software, click the Update Now or Upgrade Now button to install it.
3. Enter your administrator password, if asked. During installation, your Mac might restart, and you might see a progress bar or blank screen several times.
If Software Update says that your Mac is up to date, then no new software is currently available for your Mac model. Software Update shows only updates and upgrades that are compatible with your Mac."
If this mouse is not made by Apple, be sure to check for any pending firmware or software updates for it as well. You might need to contact the manufacturer for more details if needed.
We hope these steps can help isolate and resolve the issue so you can keep the buttons working on the mouse as expected.
Cheers!