Dir loop missing one file in specified folder - vba

Question

I've written a macro to process data within all files in a specified folder. However, it skips the first file in the folder. The problem is that the first file is referenced on this line:
FileName = Dir(path)
but the next file is referenced with this line:
FileName = Dir()
Full code:
Sub data_gatherer() 'skips ESAM_50
'Removes unrealistic data and sums the no. starts/hours run for each pump stream
Application.ScreenUpdating = False
Dim sheet As Worksheet
Dim calcSheet As Worksheet
Dim path As String
Dim ColCount As Integer
Dim StreamCode As String
Dim StreamSum As Double
Dim NextRow As Double
Dim FilePath As String
Dim FileName As String
Dim i As Integer
Dim SumRange As range
Dim SheetName As String
Dim sSrcFolder As String
sSrcFolder = "C:\IRIS MACRO TEST ZONE\SPS IRIS Bulk Data\" ' unprocessed data
path = sSrcFolder & "*.csv" 'files withing sSrcFolder
FileName = Dir(path)
Do While FileName <> ""
FileName = Dir() '''''skips first file here'''''''''''''''''''''''''''''''''''''''''''''''
FilePath = sSrcFolder & FileName
If FilePath = "C:\IRIS MACRO TEST ZONE\SPS IRIS Bulk Data\" Then ''' avoids error message for " .csv"
Exit Do
End If
Workbooks.Open (FilePath) 'error here - looks for "" filename
SheetName = Left(FileName, 10)
With Workbooks(FileName).Sheets(SheetName)
ColCount = .Cells(3, .Columns.count).End(xlToLeft).Column 'COUNT COLUMNS WITH DATA need to start with col 2
For i = 2 To ColCount 'i=2 to avoid date column
Call data_cleaner_all(FileName, SheetName, i)
Call StreamCalcs(NextRow, FileName, SheetName, SumRange, i)
Next i
End With
Workbooks(FileName).Saved = True
Workbooks(FileName).Close
Loop
Application.ScreenUpdating = True
End Sub

Answer 1

Put FileName = Dir() at the end of the loop, directly before the
Loop
line.
Edit re:
What is the difference in meaning between FileName = Dir() and FileName = Dir(path) ?
Dir(path) initializes the Dir function, and returns the first file/folder name. Dir() is always a follow-up call to a Dir(path) that came before, and returns the next file/folder.
If you call Dir() without having called Dir(path) before, you get a runtime error.