I have been having this problem and it looked like a Solidworks bug to me. I have drawn the same part 2-3 times from the beginning but it happened again.
The problem is that the derived configuration for the flat pattern somehow messes up and it shows another display state like unflattened state, or another configration display states(such as it shows the flatten pattern of another configuration instead) and i cant change it back to the correct state.
It looked to me that it might be happening when i activate the flatten pattern from the configurations panel, then use flat command there in the part file while there is a drawing file already open which has a flat view linked to that flat pattern's display state..
In drawing file, the dropdown menu of the associated view is linked to the correct configuration..I did not attach that file because it just shows the flatten pattern configuration's view which the actual problem is in the part file.You can see the problem if you activate the flatten views from the configuration menu.The second flatten view configuration is showing the not-flattened display state somehow and the flatten button is greyed out instead it should show the unflatten button as you can see from the other flattened config that works correctly as it supposed to.
If you activate the non-flattened config of the problematic flatten view and press flatten, it flattens but it does not affect/correct the display state of the problematic flattened derived configuration.I noticed it does not make a derived configuration just because you press the flatten button in part file, that seems to the reason it is not saving a corrected display state onto the flattened derived config's display state as it flattens correctly when you push the flatten button on the unflattened configuration.it seems to be creating/saving a derived config in the part file only when you make a drawing file that shows a flattened view of that part..
Anyways, is this a Solidworks bug? any idea?