When you first create footsteps for a biped in Footstep mode, they are inactive. You must activate these footsteps using the Create Keys For Inactive Footsteps button. Active footsteps have keys to animate the biped. Inactive footsteps have not been given keys by character studio.

You can make active footsteps inactive by clicking Deactivate Footsteps.

Both these buttons are on the Footstep Operations rollout.

In the Track View – Dope Sheet editor, inactive footsteps are displayed with a distinctive color to indicate they are inactive.

If you have upper body animation added to a biped, and you deactivate the footsteps, then re-activate you will lose the existing upper body keys. Use Adapt Locks on the Dynamics and Adaptation rollout to control which tracks are affected by the create keys process.