All cisco console ports are not the same that may prevent you from logging in

We are used to cisco console ports to be 9600 N-8-1 with rts/cts control. Some appliances don't support RTS, so if you set the boot up sequence but cannot get to login, playing with flow control may do the trick. If your terminal server or software gives you the status of the leads like WTI, do the port diag to see if RTS is up