Man goni's are a pain sometimes they just finicky, I've seemed to have success (so far) with feeding mine some reef roids and coral frenzy just turn off the pumps and blow some in there and then after 15 min or so put some in the pump to feed the tank.
If its been closed for a month id try moving it man maybe its the spot too, I've seen them on the sand before as long as there not covered should be good worth a try it doesn't look happy there so
just my 2 cents
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Current tank---125 gallon mixed reef 60 gallon sump, Reef octopus nw200 skimmer, Rapid LEDs, Maxspec gyre, Mp10s, Fuge, Biweekly 20% WC, QT everything
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