Mice are so cheap these days, bin it and buy a new one. More than likely the microswitch has packed up. Not worth repairing unless you are handy with a soldering iron and you've got a spare mouse to canabalise.
Xiaomi Mi Mix 2 review
What went wrong at the Designs of the Year 2017
iPhone X news: Release date, price, new features & specs
Comment utiliser Live Photos ?