The ring outside the cylinder of our lock used to be tight but after we changed the cylinder the ring spins.?

Question:please advise how to correct. what did we do wrong?

Answers:
If it is the same door , thickness is not a concern,, sounds like the screws are not tight enough. You might try a bit of thin cardboard, for a spacer. I have changed many dead bolt locks, and would suspect the screws are not tight enough,,or,,maybe a hair to long, for the thickness of that door,,so, you might use the old screws, from lock.