my CNTRLR is locked

hi I am writing this message because for some weeks my livid cntrl-r does not work ???
I do not understand where does the problem ???
when I plug my computer I was on the center line the first knob that lights up and flashes continually ....
not able to do anything and I'd really like to understand how to settle this problem because I really need my machine to work ....
hoping to have a very fast response from you thank you in advance for Touit !!!!
Sincerely Kamel.A