We replaced our engineered wood flooring with new engineered wood flooring. This was just to update the house with a fresher look. The old floor had been there for about 10 years with no issues. The new floor has been installed for about a week, furniture has not been put back. We are concerned about several hollow sounding boards that are noticeable when you walk on them. Can anyone tell us if this problem will get worse over time? How serious of a problem is this and what is the remedy? Thank you in advance for your comments and expert advice.

The spots will not get better without giving some support. There are different products that work. You drill a tiny hole and inject some epoxy into the hole. This fills the void and fastens the board down. If you have more than one spot, you drill the holes and inject some epoxy into all of them one at a time,. You can use vinegar to clean epoxy off the floor before it sets.
There are some nails that you could use that do not have heads that may work, but sometimes they will pop back up with traffic. They are the old phonograph needles, which are very hard and have a point on one end.

Thank you for the remedy. These floors were just installed by the floor company where we bought them. They are pre-finished and glued down on concrete. I would think that the process you are suggesting would mar the floors. The same company removed our old engineered hardwood floors which had no hollow places. We are thinking that the hollow areas are from poor installation, but are not sure if we should have them take up the floors and redo them. (about 1500 sq. ft.) Trying to decide if it is worth it to have them redone - huge headache because we are living in the house. Can anyone tell me what will happen to the hollow areas over time?

Every pre-finished floor that I know of has a "micro" bevel along the edges of the flooring. This is where a small, 1/8th or less hole if bored through the flooring to the hollow spot. Then a small injection tube is inserted. The epoxy is then forced under the flooring. When a small puddle is injected, the epoxy will stick to either glue or bare wood, holding the flooring down and keeping it in place.
The butt-joints are the best spots to hide the injection site.