Setting Top Value - Error 1044

I am using some code to amend the top value of some autoshapes on various sheets.
I am getting a 1004 error: unable to set the top value.

This is a stripped down part of the code, this still gives me exactly the same error

Dim shName As Variant
Dim shTag As Variant
Dim buttName As Variant

Sub GraphButtNew(shName, shTag)
buttName = "B_" & shTag
Sheets(shName).Shapes(buttName & "_1_1").Select
Selection.Top = Range("A52").Top
End Sub

Variables passed to this routine are:
shname = "Sheet1"
shtag = "SH1"

i have an autoshape called "B_SH1_1_1" on Sheet1 but it wont allow me to amend the top value