The deformation is calculated in the local coordinate space. Please note that an object's local axes may differ from the global axes. By default, objects bend along their Z-axis. If your object is rotated in any way, make sure that the Z-axis is pointing up. You can apply the rotation by pressing CTRL A on your keyboard.

Alternatively, you can check the direction of your object's local Z-axis. To do this, select your object and in the upper-right corner select Transform > Affect only > Origins.

Then, rotate the origin so that the Z axis points upwards and aligns with the global Z axis. Make sure to deactivate the Transform>Affect only>Origins option once you're finished.

Here is the Blend file:

The deformation is calculated in the local coordinate space. Please note that an object's local axes may differ from the global axes. By default, objects bend along their Z-axis. If your object is rotated in any way, make sure that the Z-axis is pointing up. You can apply the rotation by pressing CTRL A on your keyboard.

Alternatively, you can check the direction of your object's local Z-axis. To do this, select your object and in the upper-right corner select Transform > Affect only > Origins.

Then, rotate the origin so that the Z axis points upwards and aligns with the global Z axis. Make sure to deactivate the Transform>Affect only>Origins option once you're finished.

Here is the Blend file: