Unfortunately Dave is right that there is no easy fix. We were in a similar situation last year. 23K IG vinyl pool (MD, freeze/thaw zone) with 3'-4' wide concrete deck around the pool. The pool was built before we bought the house but was only 7 years old and the deck had settled and cracked in several spots. No rebar was used and the subbase was not properly filled/compacted. No stone was used underneath, only original backfill, which we found out later. The worst crack had an almost 2" raised level and was a tripping hazard. After calling everyone we could think of we had several options. Slabjacking contractor would not touch it due to the pool walls. So we could have ripped out all the deck and repoured concrete so everything matched. But of course the deck could/probably settle again. We could have replaced only the bad sections and then used sundeck or another coating to homogenize the apearance. Again, it could settle again. We decided to put in pavers as the decking. These allow water to drain through them and since the landscape slopes away from our pool, water will not collect around it and float the liner. If there are settling issues, we can pull the pavers up, regrade and replace the pavers. We have only been through 1 winter but so far no problems except that our loop-loc anchors sometimes pull a paver up a little, but it isnt a big deal. And we love the look. The cost was actually only about 10% more than repouring concrete but I think we got a good price cuz the contractor was doing this in conjuction with other work. So depending on the extent of the settling and cracking and if you are subject to freeze thaw cycles, you have a couple options, none of which are cheap and easy. If you are in a freeze/thaw zone, I was told by several contractors that original backfill around a pool like in our case (no stone) would continue to settle >30 years. Hope this helps.