Hydrology and Hydraulics: Compute pond volumes

Hi everybody !

I work with Power InRoads SS2

I have a surface with a min elevation of 27.868m and max elevation of 31.105m

I've subdivised it into several sub-basins. When I try to use the Compute pond and volumes module and insert any elevations between 29 and 30 i have a message "Pond not found at that location"

Is there a worflow to follow to obtain results ?

Thank's

Pat