MENUBAR needs to be set to 1 for the pull-down menus to display. In order to have pull-down menus to pull down, you need to have at least one pull-down menu assigned under the Menu node of your current Workspace. These are defined in one or more CUIX files that you have loaded, and are then assigned to the contents of a Workspace while customizing that Workspace in the Customize User Interface dialog (CUI command).
On the Customize tab of the Customize User Interface dialog, in the upper left pane, select the Workspace to which you want to add pull-down menus under the Worspaces node of the Main CUIx file. The Workspace Contents should display in the upper right pane. Click the Customize Workspace button to activate editing mode. Then, in the upper left pane, look through the various CUIx files you have loaded, and expand the Menus nodes. Click the box in front of a pull-down menu that you wish to add to the edited Workspace. Rearrange them as desired in the upper right pane. When finished, click the Done button in the upper right pane to exit edit mode, and then click OK in the Customize User Interface dialog to close it and save the changes.
NOTE: The ACA.cuix file does not have any pull-down menus defined. The only pull-down menu I had available in my setup on ACA 2010 was the Express pull-down from Express Tools. You will either need to build your own pull-down menus (and populate them with commands) or transfer them from the ACAD.cuix file or from a pre-ribbon ACA.cui(x) file.
You must have either transferred those pull-down menus from another CUI/CUIX file or made use of files that were briefly provided when 2010 first came out that added pull-downs and toolbars back to the ACA.cuix file. You may be able to search for and find those files as an attachment in the ACA Discussion Groups here - not sure if they work on later releases. Otherwise, you would need to transfer them from the ACAD.cuix file (you would not have any ACA commands in the pull-downs, just ACAD ones) or build your own.
I had a custom menu showing,now it is gone.
It shows up in the Customize User Interface
It is listed on the right side under menu.
Why is it missing above the ribbon ?