I found this on another page. You didn't post your model number.

"FH No water detected entering machine or Pressure switch trip not detected. If after 30 seconds the control does not detect water,
the manufacturer has assigned this error or fault code to indicate that there is a problem with the amount of water entering the machine. This error code will be displayed if the machine is trying to fill with water but the flow meter doesn’t sense any flow for 30 seconds. In this case, check the water supply to be sure you have good pressure for both hot and cold water. Then, consider replacing the flow meter. This code can also display if the machine is filling with water, the flow meter measures 10.5 gallons of water into the machine, but the water level pressure switch does not turn off the water inlet valves. If this happens the water inlet valve or the water level pressure switch may be defective. Finally, if all other things check out, the problem might be with the central control unit circuit board (CCU) or the wiring to any of these components."