We had a flood in February, due to a broken water pipe in the kitchen that seeped water into the living room area, and ruined our hardwood floor. After long discussions with the insurance company the job was given to replace the complete floor. It was replaced with Mannington Jamestown engineered hardwood. This was completed about 3 weeks ago.
Since this has been done we have noticed there seem to be "squeaks" in some areas of the floor. As well there seem to be hollow sounding spots.

The floor is a concrete base. They did a cork underlay which was glued to the concrete and then it was glued onto the hardwood. In February, moisture tests were run, holes were drilled in the walls and baseboard and fans were blowing hot air into the wall for 3 days. The original hardwood floor was not removed until early June and then the new cork and floor were installed over the next three days. I forgot to mention previously, that this is a condominium and the builders did not make a smooth even concrete surface when the original cement floor was placed.The wood was climatized in the warehouse for 3-4 days before it was brought to our home to be installed.

Should we be concerned?

Yes, I'd be concerned and have you discussed this with the installer or did you do it yourself?

No, the original floor was taken out and the new floor was installed by a professional

Call that pro back and tell him to fix the floor. Part of the issue may be the wood needed to be climatized in your home, not a warehouse. Could be other reasons to but this is why you pay a pro.

Other than pulling the floor (which I would rather not do for personal health reasons) are there other options available?