SE-HF-360 XP HIGH POWER 1kW FIBRE GLASS VERTICAL ANTENNA 80 TO 10 METRES

I replaced a Super Antenna with the SE 360 and noticed an immediate improvement. The antenna is mounted on the railing of my condo balcony, the best I can do. The only issue so far is with 20 meters: there is no apparent signal even though the SWR is 1:1. I need to contact Sigma on this.