In the Remote Desktop client settings, under the "Local Resources" tab, ensure that the "Keyboard" option is set to "On this computer" or "In full screen mode only."
or
Log in to the remote machine and check the keyboard settings. Ensure that there are no accessibility settings enabled, such as Sticky Keys or Filter Keys, which might interfere with keyboard input.
or
Ensure that your local keyboard settings are correct and that there are no accessibility settings enabled, such as Sticky Keys or Filter Keys, which might interfere with keyboard input.