From the Setup menu, select the Rates option.
On the rates screen select yes in the Show All rates drop down, then press filter.
Select the edit icon next to the inactive rate's name. You can see the status of each rate by looking at the active indicator under the rate name.
After selecting the edit icon, the rate detail will display. Change the Is This Rate Active field to yes, then scroll to the bottom of the screen and press Save.
The rate will now display in rate drop down boxes and will be active again.