Any residual adhesive or debris will prevent your screen from sealing properly.

Use the flat end of your spudger to scrape off as much adhesive as you can.

Use caution not to damage the spring connectors near the perimeter of the frame.

Use tweezers or your fingers to peel and remove any remaining adhesive.

Clean the perimeter of the frame with a small amount of highly-concentrated isopropyl alcohol (over 90%) and a lint-free or microfiber cloth.