Found the fix for this, I had noticed this error message before but thought it was related to the dropdowns

"Message: Sys.ArgumentNullException: Value cannot be null.

Parameter name: panelsCreated[1]"

I finally searched on that error message and ran across several posts saying to put ScriptMode="Release" into the markup, example below, the drop downs work now 🙂

<asp:ScriptManager ID="ScriptManager1" runat="server" ScriptMode="Release">

</asp:ScriptManager>