Check the official Facebook Help Center or comment below with the exact error message you see on your desktop screen.
Many users need to access more than one Facebook account—for example, a personal profile and a business page manager. While Facebook’s terms technically restrict multiple personal accounts, here is how legitimate users can switch between profiles and pages. facebook login desktop
Caps Lock is on, the keyboard layout has changed, or you have a stray space in your password. Check the official Facebook Help Center or comment