How to use CM21 transaction to dispatch Production orders?


Can anyone tell me what settings are required before a Production Order can be dispatched in CM21? I have tried doing it by drag and drop method and also by hitting the Dispatch button, but I receive 'Invalid Function, each time.

I am fairly new to Capacity levelling, hence any advice on it will be highly appreciated. I have read the standard SAP document, but it doesnt focus on specific setting required!

Attached is a snap of our CM21 screen. We use 2 Capacity category (Labour & Machine)

Thanks in advance