Martin Logan Sequel II cross over problem ưith bass

Help neededI have a pair of Martin Logan Sequel II stored for 20 years. Recently pulled out. I found that one speaker has no bass. I opened the power box, The bass speaker tested 4 Ohm. The electrostatic plays fine. So it seems that the cross over gives no output for the bass section. Martin Logan does not provide a schematic, I need help. Anyone had this problem before?