I doubt I can help you here as I don't know much about gyros, but I guess it's possible that your console has a different gyro version, a different gyro number (from what I expected) or something wrong with the gyro itself. As a last resort, please try this slightly modified Sono and Gericom's old testing program. Just start it as a regular NDS game. On the top screen there is a line that goes from the center to another place. Ideally, if the gyro works, you should be able to move its end by tilting the console. Furthermore, there are several numbers on the bottom screen. Copy them here. Launch this app several times to make sure the values are "stable"I will probably give up on gyro unless you would find it helpful to get more data on reproducing this issue on other versions.
By the way, what OS and console version do you have?