Make sure you mix the paste as per instructions on the packet adding to much water can weaken the strenght of the paste.
Lining paper needs the least amount of soaking in time but still needs a good 5 minutes before you put it on the wall, never put it strait on the wall after pasting.
Once you've pasted the lining paper, in the 5 minutes soaking time, it expands. Once on the wall it starts to dry and contracts leaving you with a tight finish on the wall, if the paste mix is weak the contracting pulls the seems apart.
Is it loose, bubbled up off the wall?