To repair a lifting wallpaper seam, you will need the following supplies: a putty knife, painter's tape, spackling paste, and a damp cloth. 1. Use the putty knife to carefully remove any loose bits of wallpaper around the seam. 2. Apply painter's tape to both sides of the seam to create a barrier between the wall and spackling paste. 3. Apply spackling paste over the seam using a spoon or your fingers. 4. Smooth out the spackling paste using a damp cloth until it is even with the surrounding wall surface. 5. Let the spackling paste dry completely before removing the painter's tape.

First, try gently pushing down on the seams to see if they adhere better to the wall. If that doesn't work, you can use a wallpaper seam sealant or even elmers glue to re-adhere the wallpaper. Finally, if that still doesn't do the trick, you can use a razor blade or X-acto knife to cut away the excess wallpaper and create a new seam. Just be careful not to cut into the wall itself!