Transmission

I have a 2008 gmc Sierra I've been having issues
with getting into reverse and passing thru reverse
to get into park on occasion. Then when I do
reverse u would hear a fast clicking coming from
the transmission. This morning I go to leave for
work and the truck won't move . I've tried adjusting
the cable, I've tried shifting manually from
underneath, I can put it into gear kill it and won't
start back up, put it in neutral and am able to start
it.
I was thinking it was the cable but the cable seems
to be working fine, isn't there a solenoid inside the
transmission that may be causing my problem?