Your code works in Word 2019, assuming there are two tables in the document. It adds a copy of the table to the bottom of table 2. You can do it without the paste if you wish e.g.
Code:
Private Sub CommandButton1_Click()
Dim oRng As Range
Dim oFld As FormFields
Dim i As Long
If ActiveDocument.ProtectionType <> wdNoProtection Then
ActiveDocument.Unprotect
End If
With ActiveDocument
Set oRng = ActiveDocument.Tables(2).Range
oRng.Collapse wdCollapseEnd
oRng.FormattedText = ActiveDocument.Tables(2).Range.FormattedText
Set oFld = oRng.FormFields
For i = 1 To oFld.Count
oFld(i).Select
If oFld(i).Type = wdFieldFormDropDown Then
oFld(i).Result = oFld(i).DropDown.ListEntries(1).Name
Else
oFld(i).Result = ""
End If
Next
End With
ActiveDocument.Protect Type:=wdAllowOnlyFormFields, NoReset:=True
End Sub