Workbook.Open can not find the file - excel

Question

I am running the following code. The code is for finding some particular values in all the Excel sheets in a folder.
It gives me the error
"Sorry, we couldn't find the file. Is it possible it was moved, renamed or deleted?"
when it executes
Set wbSlave = Workbooks.Open(filename:=myfilname)
Please help.
Sub find_cells()
Dim i, j As Integer
Dim cell_content As String
Dim total_values As Long
Dim cell_location As Range
Dim cell_address As String
Dim sht As Worksheet
Dim myfilname As String
Dim fldrpath As String
Dim wbMaster As Workbook
Dim wbSlave As Workbook
Dim currentfilename As String
Set wbMaster = ThisWorkbook
j = 3
total_values = Application.WorksheetFunction.CountA(wbMaster.Sheets("Engine").Range("A:A"))
fldrpath = "C:\test\"
myfilname = Dir(fldrpath & "*.xls*")
Application.ScreenUpdating = False
Do While myfilname <> ""
'myfilname = Dir()
Set wbSlave = Workbooks.Open(filename:=myfilname)
For Each sht In wbSlave.Sheets
For i = 2 To total_values
cell_content = wbMaster.Sheets("Engine").Range("A" & i).Value
With sht.UsedRange
Set cell_location = .Find(cell_content, LookIn:=xlValues, MatchCase:=False, SearchFormat:=False)
If Not cell_location Is Nothing Then
cell_address = cell_location.Address
Do
wbMaster.Sheets("Sheet1").Columns(j).Value = cell_location.EntireColumn.Value
j = j + 1
Set cell_location = .FindNext(cell_location)
Loop While Not cell_location Is Nothing And cell_location.Address <> cell_address
End If
End With
Set cell_location = Nothing
If i = total_values Then Exit For
Next i
Next
myfilname = Dir()
Loop
End Sub

Answer 1

The Dir function returns only the matching filename - no path. Then if you try to open it and you are currently not in a correct folder, you get this error.
Set a watch to the variable myfilname or just add Debug.Print myfilname and you see it right away.
https://learn.microsoft.com/en-us/office/vba/language/reference/user-interface-help/dir-function