What I do if the display says err 01

I own a used canon eos 50d. I manage to use it about 4 months before the display suggest an err 01 had occur and it has to do with the connection between the lens and camera. What's gone wrong and what should i do because as i consult canon service, they say it cannot be fix because for canon 50d, there are no spare part available anymore because it is too out dated. What option do i have@ any good suggestion.