Hello Birdzilla and welcome to the family, so glad you decided to join us and we look forward to hearing more about you and your grey, btw what is his name?
If this is a rehomed grey no wonder you are having problems with him and if you don't know what his former home life was like then that makes it even more difficult to understand him.
It will take time for him to learn to trust you and bond with you so be very patient with him, continue to talk to him and offer him treats and do not give up, he needs you to be there for him.
Take some time and read thru the many threads for lots of useful and helpful information and do not hesitate to ask questions you may have. We will do our best to get you some answers and help you in any way we can.
If you have some pictures you would like to share with us we would love to see him.