Fault 39 refers to the water level sensor. The pressure tube runs from an air dome at bottom/side of the tub up to the pressure sensor on the control board. A small hole in the tub wall is open to the air dome. Air pressure trapped in the tube increases as water rises in the tub for sensing the level.

Check if the tube is perhaps pinched or kinked (it runs into the console with the wiring harness at the right/rear corner of the cabinet). Examine the full path of it from the air dome to the control board. You may notice what appears to be a wire inside it ... there's no electrical connection involved, I believe the wire is to help prevent kinking toward the board end.

Less common, the tub opening to the air dome may be clogged with debris (requires pulling the inner basket for access). There's also a seal at bottom of the air dome, held on with a clip, which can be removed to clean in there.

If everything physically checks-out on the air dome and pressure tube, then the pressure sensor on the control board may be bad, in which case the board must be replaced. The pressure sensor is part-and-parcel of the board.