Hi Uri,
I set up a KL27 running a small loop with a printf so I could see that it was executing.
I was able to connect to the target although it complained about thread list which I don't understand. The debugger display was also not initially synchronized so it could certainly do with some improvement.
It is possible that it cannot connect to a target due to a few reasons such as disabled debug interface pins or the target has halted with a bus fault. The only reliable connection process is with a target reset and even then it may not be possible.
Other than that I can't really suggest a reason.
bye