I came to this thread in hopes of finding the solution. Instead, I figured out my (mom's) problem, and thought I'd share in case it helps others. So...it's your mouse. I know, I know. "How can it be my mouse if my touchpad/other mouse doesn't work?" Well, I'll tell you my story, and you can decide.
Mum was using her work laptop (Lenovo Thinkpad) with her own mouse, a Logi M720...and she spilled coffee on the mouse. It didn't die immediately, but at a certain point hours later and after she switched to her personal laptop (a "consumer grade" Lenovo), she began to have the problem everyone here describes: Mouse will move the pointer, but you can't click anything. Indeed, even when she switched off the Logi mouse, both her backup corded mouse and the "clickpad" exhibited the same behaviours: Pointer yes, clicky no.
She had already tried restarting, as well as changing the channel of the mouse-computer Bluetooth connection, which didn't help. I initially tried the Ctrl+Alt+Del trick, which didn't work for long at all. At a certain point, though, I did Ctrl+Alt+Del while the Logi was switched off, and voilà! The corded mouse and touchpad started working again. I tried fixing the mouse with penetrating lube (e.g. WD-40), which I thought had fixed it, but it stopped working as I was typing this comment (I'll need something better at displacing water...maybe 99% iso). Even so, the click on the corded mouse and clickpad both work properly.
So, in short:
- turn off your suspect mouse by the switch (if cordless) or unplug it,
- (if it's Bluetooth and you don't use a dongle) go into Bluetooth devices and "Remove device", and
- then do Ctrl+Alt+Del
and see if that sets you right. If your "mouse" is in fact a laptop's clickpad (touchpad), you'll need an external mouse of some kind to test this. This was easier on mum's home computer because it's touchscreen (never thought I'd be happy about it), but I assume you can do the same with Windows key, arrow keys and Ctrl+Alt+Del. Hope this helps.