为何我的vba中使用ado的时候会出现灾难性的错误8888ffff？

Question

代码如下：Sub Find_ADO()    '不同工作薄Dim thConn As Object
Dim thRst As Object
Dim i, n As Integer
Dim mSql As String
Dim nowvalue As String
Dim dirpath As String
Dim fullname As Stringdirpath = ThisWorkbook.path & "\test"
'MsgBox dirpath
    
    With Sheets("Sheet1")
        For i = 2 To .[a65536].End(xlUp).Row
            Set fs = Application.FileSearch
            nowvalue = .Range("A" & i)
            
            With fs
                .LookIn = dirpath
                .SearchSubFolders = True
                .filename = "*.xls"
                If .Execute() > 0 Then
                    'MsgBox "There were " & .FoundFiles.Count & " file(s) found."
                    For n = 1 To .FoundFiles.Count
                        Set thConn = CreateObject("Adodb.Connection")
                        Set thRst = CreateObject("Adodb.Recordset")
                        thConn.Open "Provider=Microsoft.Jet.OLEDB.4.0;" & "Data Source=" & .FoundFiles(n) & ";" & "Extended Properties=""Excel 8.0;HDR=YES;"""
                        mSql = "select mfg from [wt1951a$] where barcode = '" & nowvalue & "'"
                        Set thRst = thConn.Execute(mSql)
                        If thRst.EOF = False Then
                            Sheets(1).Cells(i, 2).CopyFromRecordset thRst
                            thRst.Close
                            thConn.Close
                            Set thRst = Nothing
                            Set thConn = Nothing
                            Exit For
                        Else
                            thRst.Close
                            thConn.Close
                            Set thRst = Nothing
                            Set thConn = Nothing
                        End If
                    Next
                Else
                    MsgBox "There were no files found."
                End If
            End With
            
            Set fs = Nothing
        Next i
    End With
    
End Sub