extract range has a missing or illegal field name

I reused some of Jindon's code so hopefully it works the first time.
If you have any problems copy and paste the line of code that errors, it will be the one highlighted in yellow.
Try this on a copy.

Sub ImportWorksheets()
Dim ws As Worksheet, a, i As Long, myName As String, dic As Object, arrFiles, j, wbSrc As Workbook
Application.ScreenUpdating = False
    Set dic = CreateObject("Scripting.Dictionary")
      With Sheets("sheet1").Cells(1).CurrentRegion
        a = .Columns("g").Value
        For i = 2 To UBound(a, 1)
            If Not dic.exists(a(i, 1)) Then
                dic(a(i, 1)) = a(i, 1) & "_" & Split(.Cells(i, 6).Value, ",")(0) & ".xlsx"
            End If
        Next
        arrFiles = dic.items()
        For Each j In arrFiles
            If Dir(ThisWorkbook.Path & "\" & j) <> "" Then
                Set wbSrc = Workbooks.Open(ThisWorkbook.Path & "\" & j)
                wbSrc.Worksheets(1).Copy After:=ThisWorkbook.Worksheets(ThisWorkbook.Worksheets.Count)
                wbSrc.Close
            End If
        Next j
    End With
Application.ScreenUpdating = True
End Sub