SSRS Report Builder Date filter did not work.

I have this expression where i put it in the @endDate parameter expression in Default Value parameter.

=FormatDateTime(Parameters!endDate.Value,DateFormat.ShortDate)

However, i keep on getting this error,

The DefaultValue expression for the report parameter ‘endDate’ contains an error: The expression that references the parameter 'endDate' does not exist in the Parameters collection. Letters in the names of parameters must use the correct case. (rsRuntimeErrorInExpression)

Can anyone please explain to me what i did wrong here?i check on the related @endDate,but there is no wrong case.

Or should i put it in the Availabe Value?