There is not enough resistance in the flywheel regardless of damper setting.
You may not be generating enough power on the drive to feel resistance from the flywheel. The indoor rower generates resistance through moving air. The more air the fan moves, either by turning faster or by having more air available because of a more open damper, the harder it will be to spin the fan and the harder the resistance will be. By increasing your work output on the drive, you will be increasing your resistance. This can be proven out by doing the following: Try rowing at a low stroke rate (16–20 spm) and concentrating on rowing each stroke separately with lots of power on the drive, pushing hard with the legs. Try rowing like this at a damper setting of 10 for a minute or two, then 5 for a minute or two, then 1. Click for more technique help.
The flywheel is dusty and needs to be cleaned out.