Key stuck down onto keyboard

Last night, my mom spilled a drink onto her keyboard. Laptop still works, so right now I'm removing the keys to clean up any residue the drink left. After I finished cleaning one of the keys, I tried to place it back but it keeps pressing completely down onto the keyboard unlike other keys where you can still press it. I took it off and check to make sure everything was in place and it seems right to me, so I'm not sure what is causing the problem. Can anyone help?