ailure to Start blowing CAL2 fuse (black fue on top of +ve battery terminal?

my sedan cuts out when starting. I bought a new battery and replaced the old one. I also replaced a blown CAL 2 fuse( main black fuse on top of battery positive terminal) with a new a new one. Upon pressing the start button, the dash flicked and went blank, failing to start completely.
All electrics is not working (windows, lights, dashboard, clock timer etc).
What could be the problem???