I don't know why your code is getting an error, but there is a better way to achieve what you want without using the clipboard.
Code:
Sub COPYPAR()
'Copy a range from the current para's start till after "=" and
'add it after the para.
Dim selRng As Range: Set selRng = Selection.Paragraphs(1).Range
Dim copyRng As Range: Set copyRng = selRng.Duplicate
'make sure that = is found
If Not copyRng.MoveEndUntil("=", wdBackward) = 0 Then
'make sure that the = is in the same paragraph
If copyRng.InRange(selRng) Then
selRng.InsertParagraphAfter
selRng.Collapse wdCollapseEnd
selRng.FormattedText = copyRng.FormattedText
End If
End If
End Sub