Why do meters for variables in W units get ignored?

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In my EnergyPlus model, I have created several Meter:Custum objects to sum several output variables.

Some of them [The ones that are rates and so in W units] return a warning message and the meter is ignored in the output data.

The message:

** Warning ** DetermineMeterIPUnits: Meter units not recognized for IP Units conversion=[W].
   **   ~~~   ** ..on Meter:Custom="TEST6".
   **   ~~~   ** ..requests for IP units from this meter will be ignored.
   ** Warning ** Meter:Custom="TEST6", variable not summed variable Output Variable or Meter Name="PLANT SUPPLY SIDE COOLING DEMAND RATE".
   **   ~~~   ** ...will not be shown with the Meter results; units for meter=W, units for this variable=W.
   ** Warning ** Meter:Custom="TEST6", no items assigned 
   **   ~~~   ** ...will not be shown with the Meter results. This may be caused by a Meter:Custom be assigned to another Meter:Custom.

The custom meter object:

Meter:Custom,
    Test6,                   !- Name
    Generic,                 !- Fuel Type
    *,                        !- Key Name 1
    Plant Supply Side Cooling Demand Rate;  !- Output Variable or Meter Name 1

I have used the following object to set unit conversion:

OutputControl:Table:Style,
    All,                     !- Column Separator
    JtoKWH;                  !- Unit Conversion

I would like to understand I do I get this error and the meters. Why is this? Shall I set a different unit conversion?