Mine are set to Width=10 Contrast=20%
I think your width is too low, the tool will not look beyond 1 pixel from where your cursor is. You may want to bump up your contrast as well but this will depend on the picture.
To specify a detection width, enter a pixel value for Width. The Magnetic Lasso tool detects edges only within the specified distance from the pointer.
To specify the lasso's sensitivity to edges in the image, enter a value between 1% and 100% for Edge Contrast. A higher value detects only edges that contrast sharply with their surroundings; a lower value detects lower-contrast edges.
To specify the rate at which the lasso sets fastening points, enter a value between 0 and 100 for Frequency. A higher value anchors the selection border in place more quickly.
Good luck, Jimmy