This happened to me last week on the same day as you posted your question, spooky!
To fix it I found [link|https://www.geekiest.net/post/Fix-Logitech-MX-Master-2S-cursor-not-moving|this|new_window=true] repair guide, which suggests that the gesture button can get stuck if it gets pressed... wrong.
I used [guide|140395|this|new_window=true] teardown guide to open the mouse up with an iOpener to soften the sticker adhesive and a metal spudger to peel it up, then broad tweezers to prevent tearing or grease from my fingers, I followed Steps 1-2. Then the first part of Step 3 to remove the black screws. I tested the button and its mechanism. Both seems to actuate fine, so I reattached it without tightening fully to give it a little wiggle room.
Once I reassembled the mouse and used the iOpener to soften the adhesive and smooth it back down the the metal spudger, it worked as good as new, if a little more crinkly on the bottom, which is undetectable in normal operation.