first off it is not glue it is a special Adhesive made by 3M called 300SLE
DO not make the mistake of GLUING your case back together. First, take a blow dryer or heat gun if you have one. and on low move it back and forth in the area that has come unglued. then using your finger carefully press and hold the pieces back together. If you have a potato chip clip or other holder or sit a book or two on it with a pillow between it.
Look on ebay they sell the stripes of adhesive you need if that fail replace it if you can find a ifitit.com guide to doing that