Custom ribbon button action always disabled when command is defined

I want to add new button to the ribbon in Pages library. To do so, I have following code:

<CustomAction Id="Ribbon.PublishTab.Publishing.Actions.UploadDocumentButton" Location="CommandUI.Ribbon">
    <CommandUIExtension>
      <CommandUIDefinitions>
        <CommandUIDefinition Location="Ribbon.EditingTools.CPInsert.Links.Controls._children" >
          <Button Id="Ribbon.PublishTab.Publishing.UploadDocumentButton1" Command="Test1"
                  Image16by16="/_layouts/15/Solution/Images/Al_16_by_16.jpg"
                  Image32by32="/_layouts/15/Solution/Images/Al_32_by_32.jpg"
                  LabelText="Upload File" TemplateAlias="o1" Sequence="100" />
        </CommandUIDefinition>
      </CommandUIDefinitions>
      <CommandUIHandlers>
        <CommandUIHandler Command="Test1" CommandAction="javascript:function Action()
                          {
                            alert('hello');
                          } 
                          Action();"  EnabledScript="javascript:function JustReturnTrue(){  return true}JustReturnTrue();" />
      </CommandUIHandlers>
    </CommandUIExtension>
  </CustomAction>

The ribbon button appears on proper place. But it is always disabled. After try things, I figured out that when I remove command attribute from <Button> tag it is getting enabled but when I place the same attribute and deploy, it is getting disabled.

What am I missing?