My problem is in painting the conic 3-6-9 dB loudspeaker coverage patterns on the seating area. I get the magenta line indicating the aiming angle, but I am not able to turn on the patterns even though the program says the beam patterns are on.

If the Options are shoing 3,6,9 dB Cones ON and the magenta line is visible, check also the currently used frequency under Options, maybe the current band is not valid. Otherwise you should also check if there are really cones with values different from 0° and 180° using the Speakerbase.