Lost ESN number in Kenwood Radio

Question

My Kenwood radio in my car lost its esn number when my battery went dead. Now I can not connect to my Sirius Radio account. I do have the esn number that was set up originally with Sirius for the radio. Sirius says the radio needs to be replaced - my question is - can this be fixed or does the radio have to be replaced? (The Radio is 3.5 years old and out of warranty.)