Screen not responding to touch after change

Hi,

I have just changed a screen on a alcatel 1 model. Number 5033. The new screen worked fine when I tested it. I put it in place with adhesive it still worked fine. As soon as I put the rear chassis on the screen stops responding . Take the chassis off and it works. The chassis is plastic the only metal is the camera ring at the top. I have tried pushing the flex in hard but the screen still responds fine , I have put kapton tape over the flex and then the chassis but still no good. Has anyone else had this problem and if so how did you overcome it. The chassis needs to be on or the back cover wont stay on etc

Thanks