One of these will definitely do the trick
Fix Left Mouse Button Not Working Issue in Windows 10
Left mouse button is the default command for selecting and highlighting items on a computer. If the left mouse button on your mouse or trackpad is not working as intended, the problem could be a software or hardware related glitch.
If you are using an external mouse, the left mouse button may not function properly if foreign particles (dust, dirt, etc.) are stuck in the mouse. Contact the mouse manufacturer, visit their website, or refer to the product manual for cleaning instructions. However, if the left mouse button is not working on your PC's touchpad and/or external mouse, try some of the solutions below.
You will need an input method/device to implement some of these troubleshooting solutions. For example, if your PC doesn't have touch, try different external mice and see if one works with your PC. You can also use your keyboard to select items and navigate Windows if Mouse Keys is enabled on your PC.
