If you have an Omni / Magnitude the outdoor kitchen sink is plumbed so that is below the gray tank so the macerator pushes the water from the sink to the gray tank. There is also a directional valve to prevent the shower drain from backwashing into the outdoor kitchen sink.
As was mentioned, you should start looking at 12v power. You should check the fuse in the power distribution panel. You can also open the access door below the sink and make sure the wires connecting to the macerator pump are connected properly.
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