Hello Mark and welcome to our family, we are so glad you could give this new to you grey a new home.
This is just the first weekend right, give the bird some time to settle down for we are talking about a mature bird that has baggage that could be hard to deal with but in time it will become easier, just be patient with him and good things will come with lots of patience.
I doubt he is not stepping up because of his handicaps for he probably doesn't even know he isn't like other birds, he is just unsure of his new surroundings after all he is in a completely new to him environment and being a mature bird will take him longer to adjust.
It sounds like you are doing all the right things for now, include him in the goings on in the house, talk to him a lot and just be there for him and you will gradually see him show more of his true personality, for right now he is a little guarded.
Do read thru the many threads for lots of useful information and ask questions you may have and we will do our best to get you some answers.
We would love to see some pictures of S, is that his real name, if you would indulge us.