Motion Builder- help importing .c3d data, marker issues

I am new to motion capture and Motion Builder. I have recorded the .c3d data but am having trouble getting the markers to import correctly.

The markers only appear when I leave the ‘Create unused optical segments’ box ticked. I’m then not able to select the markers to create a Marker Set to attach to my actor.

I’m really struggling to work out what I’m doing wrong- is there some setting I need to change or something wrong with my .c3d files?

Any help would be massively appreciated.

Thanks,

Louise.