Well Marian, you need to mention the exact model of your USB mouse for me to solve your issue. I can give some general tips to you here and you can try and see if any of the proposed solution works for you or not.
First, you need to uninstall the driver of the USB mouse and then reinstall the driver. It usually helps in most cases.
If it doesn't help, then you can try to download a latest driver for your USB mouse from the A4Tech website. They have all the updates and patches available there. Installing a new version will definitely help.
The cause can also be due to a conflict in ports. May be some other devices are interfering with it so that's why it is not working properly. However, if you can give me the exact model of your mouse, i will post the links to the drivers so that you can directly install them.
If that problem was with a wireless mouse and it stopped working, the first thing you need to check is the battery. All wireless mouse use battery as a source of power since it doesn’t have a cable that connects directly to the computer that can feed power to the device.
Most wireless mouse are sold with the battery included but there are ones that don’t include the battery in the package like the one I bought from a nearby store. Now, if your wireless mouse stopped working, check if the battery is drained. Open the battery compartment at the bottom then replace the battery with a fresh one.
If this doesn’t work, try transferring the USB adapter to another USB port. If this doesn’t work, use a wired mouse instead.