Experiencing same issue! This just started today. It worked just fine up through yesterday, for the last 2 years. I have never had this issue. My scroll wheel works perfectly fine in all other browsers and programs. I have a logitech mouse, but no logitech smooth scroll extension to remove (as has been suggested). Tried turning off/on most of my extensions to no avail. Also rebooted PC-no change. I can easily scroll within this forum page, as well, just not when viewing or working within a sheet. A little guidance from smartsheet on this would be helpful.