Thanks for posting your question!
It sounds like the LCD cable in your replacement screen is either damaged, or improperly positioned. Can you tell me where you got the display assembly from? If you did not source from a legitimate established supplier (such as iFixit) then you may have a part that is either faulty or particularly prone to this type of failure from the cables not having the "correct" amount of flex in them. Some of the lower quality displays have flex cables that will easily cause the display to not function properly when an increased amount of bend is put on them, such as going from open to closed when installing the display assembly.
I hope you find this answer to be useful. Please be sure to ask if you need further help or clarification!