if there are blanks
Change
If Bcell.Value <> Empty Then
to
If Bcell.Value <> "" Then
Or to
If Len(Trim(Bcell.Value)) <> 0 Then
The Empty
keyword is used as a Variant
subtype. It indicates an uninitialized variable value.
Your code can be written as
Sub Sample()
Dim x As ListObject
Dim z As Range
Dim Bcell As Range
Set x = ActiveSheet.ListObjects("Table6")
Set z = x.DataBodyRange.Columns(11)
For Each Bcell In z.Cells
If Bcell.Value <> "" Then
Run "InsertNAtoBlanks"
End If
Next
End Sub