Read the above again, (By BomberHarris) with reference to para 6, the nosewheel disengages from the steering when extended. (cessna and piper singles).
It suggests that you are lowering the nosewheel too rapidly, or letting it hit the ground of its own accord.
When it first touches, if done gently enough, it will free-caster, and as the oleo compresses, so the nosewheel steering will engage.
When I did a Beagle pup rating, I found x/winds a bugger at the point of nosewheel touchdown. The aeroplane is extremely controllable, but I couldn't avoid some side-force on the nosegear when it touched in a decent crosswind. My instructor said not to worry about it too much. That said, there is repeated advice above to keep flying the aeroplane. Do it.
Solve the problem once and for all by flyng an AA5.Fully castering nosewheel.