Diamond blocks can be used as elevators to get between floors without needing ladders or other holes in your floor!
For most Players the range is 4-12 blocks
For players who are Prestige 1 Warlock+ or Prince+ that range extends up to 24 blocks
Jump to go up
Crouch to go down
Check that the elevators are within range of each other and are directly above/below one another
Check that there is nothing blocking the elevator. There must be 2 blocks of air above an elevator for it to function. Even signs or torches can prevent an elevator from working.