Click imagem Button with iframe

Dear , good day.

Need to click a button , but I can not at all.
Below is what I need button click

I need click herer: window.document.getElementById("btnAtivo").src = "../images/botoes/bt_ativo.gif"

I tried:

idoc.document.document.getElementById("btnAtivo").click
idoc.document.document.getElementById("btnAtivo").onclick

Set ElementCol = Idoc.document.getElementsByTagName("img")

For Each elea In ElementCol

If InStr(elea.innerHTML, "../images/botoes/bt_ativo.gif") > 0 Then
elea.Click

Exit For

End If

Next

If you can help me thank you .

code below: