My arrow keys cant hold more than two notes at a time

[DDR_M45T4]

my old computer didnt have this problem but with my new one if I press more than two arrows at the same time the game wont read it. this is a problem since a lot of my stepmania songs require you to press more than two keys at a time especially with holds, then I lose big time on my score.
my computer is an old macbook but my Acer PC worked fine with all the arrows. is there any way to fix this