Serial terminal not taking keyboard input
Usually this means that either:

(a) the target device is not sending back any response to your keystrokes

or

(b) your flow control settings are incorrect

or

(c) you have a defective cable.

If (b) is the case, you'll to make sure that the settings XON/XOFF, RTS/CTS and DTR/DSR are set correctly. You can just try flipping them manually, as nothing "bad" happens if you set them incorrectly (except not being able to send/receive data).

If (c) is the case, try with a different cable. It is possible to have a cable that only works in one direction due to a hardware problem.