You need the orientation of the sensors if you want to be able to process them correctly… You don’t have this information? If you set the Orient field to a random value (eg. [1;0;0]), you’d be able to plot 2D/3D topographies, but not to do any source reconstruction.
Pay attention to the type of the sensors: MEG MAG (sensors ending with “1”) or MEG GRAD (sensors “2” and “3”).