1. Check the CLOCK setting. The FBQ1024 will need to be in 48K or 44.1K CLOCK position. If this is set to 96K, the FBQ feature is not accessible.
2. The TRUE RESPONSE mode is less suitable for the specific purpose of feedback suppression. The CONSTANT Q filter option is likely to be more effective, give this option a shot and see if the results differ/improve.
3. If the lights are not illumintated, then the input signal to the DEQ may not be sufficient to "trip" the LED's and feedback circuit. Try increasing the input signal to the DEQ and adjusting the associated power amplifier down to compensate for the increase in volume if necessary.