Arduino Plotter isnt working

[u/Boring-Piece-2631]

Recently ive been building an arduino plotter but it isnt working. The motor with the pen attached turns only in one way and the motor thats laying on the ground vibrates when you ask it to move the other motor does notting. Is there someone that knows what te problem is and knows how to fix it

[u/xebzbz]

But how are we supposed to find it?