My mission planner is not letting me set modes at the time of initial configuration, the drop down box does not show any options to select from..(check attached pic) has anyone similar problems? Any idea how to solve it

I think you could fix it by reinstalling the software !

Reinstall the firmware and check the channel fixed for flight mode bro...

Just need to press Ctrl+F and select Param gen, then on restarting Mission Planner problem is fixed