Do you have the Silver Armour? There is no limit on when this can be done, except that you first need the treasure maps and silver armour (and it must be done before you move the wastelands, as you can not return after that).Silver Armour and Treasure Maps
Are you still playing the character that had the problem with Rak'Sheen? Maybe whatever caused that is interfering with this quest?
You may be able to use the teleporter stones to get over the mountain, or hex teleport in.
Check your messages (click 'My Stuff' in the top menu bar, then 'My Messages').