What is the best way to: How can I repair an opening that is widening in wall paper?
Reactivate the paste around the gap with a rag soaked in warm water hold the rag over the area for a minute or two, and then carefully open the gap a little larger so you'll have more room for the sealer then squeeze seam sealer (white glue works in a pinch) into the gap, and press the paper to the wall with a roller clean excess sealer with a sponge.