Very Strange SqlClient error with SmallDatetime parameter in SQL Server 2014 stored proc

I've been stumped with the following error for the past hour:

"Procedure or function 'write_call' expects parameter '@Date', which was not supplied."

The @date parameter is a smalldatetime. I am trying to pass the value #1/27/2009 04:32:00 PM#

I am using SQLExpress 2014.

The same stored proc has been in production on SQLExpress 2008

T-SQL Stored Proc:

 ALTER proc [dbo].[write_call]
(
    @Date smalldatetime, @Duration smallint, @Ring tinyint, @Extension smallint = null, @Number varchar(20) = null, @LineID smallint, 
    @AccountID smallint = null, @AccountName varchar(30) = null, @UnitID smallint = null, @UnitName varchar(30) = null, @AreaName varchar(100) = null, @CallType char(1) = null,
    @CallCode varchar(6) = null, @Rate numeric(5,2) = 0.0, @Cost numeric(12,2) = 0.0, @TAC varchar(10) = null
)

as

declare @id int=0, @old_acctid int=0  --, @old_rate numeric(5,2)=0.0, @old_cost numeric(12,2)=0.0

select @id=o.ID,@old_acctid=o.AccountID from OutboundCalls o where o.Date=@Date and o.Duration=@Duration and o.Number=@Number

if @id=0
    begin
        insert into _OutboundCalls (Date, Duration, Ring, Extension, Number, LineID, AccountID, AccountName, UnitID, UnitName, AreaName, CallType,CallCode, Rate, Cost, TAC,redirected,contactid,CompanyID,CompanyName)
        values (@Date, @Duration, @Ring, @Extension, @Number, @LineID, @AccountID, @AccountName, @UnitID, @UnitName, @AreaName, @CallType, @CallCode, @Rate, @Cost, @TAC,1,0,1,'PricewaterhouseCoopers')
    end
else if @id>0 and @old_acctid<>@AccountID
    update OutboundCalls set AccountID=@AccountID, UnitID=@UnitID,AccountName=@AccountName,UnitName=@UnitName
    where OutboundCalls.ID=@id

VB.NET 2015:

Private Sub write_call(c As CallInfo)
    Using cnn = New SqlClient.SqlConnection(connString)
        Using cmd = New SqlClient.SqlCommand("write_call", cnn)

            cmd.Parameters.AddWithValue("@Date", c.dt)
            cmd.Parameters.AddWithValue("@Duration", c.secDurn)
            cmd.Parameters.AddWithValue("@Ring", 0)
            cmd.Parameters.AddWithValue("@Extension", c.src)
            cmd.Parameters.AddWithValue("@Number", c.dst)
            cmd.Parameters.AddWithValue("@LineID", c.lineId)
            cmd.Parameters.AddWithValue("@AccountID", c.account_id)
            cmd.Parameters.AddWithValue("@AccountName", c.account_name)
            cmd.Parameters.AddWithValue("@UnitID", c.unit_id)
            cmd.Parameters.AddWithValue("@UnitName", c.unit_name)
            cmd.Parameters.AddWithValue("@AreaName", c.area?.Name)
            cmd.Parameters.AddWithValue("@CallType", c.dst_type)
            cmd.Parameters.AddWithValue("@CallCode", c.callcode)
            cmd.Parameters.AddWithValue("@Rate", c.rate?.rate)
            cmd.Parameters.AddWithValue("@Cost", c.Cost)
            cmd.Parameters.AddWithValue("@TAC", c._oC)

            cnn.Open()

            Try
                cmd.ExecuteNonQuery()
            Catch ex As Exception
                Stop
            End Try
        End Using
    End Using
End Sub

It seems that your code misses to set the CommandType property. This property defaults to CommandType.Text and it is appropriate when you pass a sql string as the CommandText.

If you pass the name of a stored procedure you need to set

cmd.CommandType = CommandType.StoredProcedure

without this setting the behavior of the SqlCommand is unpredictable.