Hi Ayman,
The "Combine Cases" macro is not designed to work with sub-hourly simulations. If you are using weather files with subhourly (15-minute, 30-minute, etc.) data instead of hourly data, you will have to switch to a weather file with hourly data.
If you are not using subhourly weather data, please attach a copy of your .sam file so I can investigate.
Best regards,
Paul.