Phone and Tablet plan missing on Muse

[troys29392294]

I am missing the plan pages for the Phone and Tablet on all my sites. Here is some screen shots.

[Günter Heißenbüttel · Accepted solution]

• You can‘t add alternate layouts, because they are already existing! Consequently the „Add Alternate Layout“ options are dimmed.
  If you don’t find the buttons „desktop“, „tablet“ and „phone“ at the top of the workspace  in plan view,
• you have perhaps hidden the upper control bar unintentionally. Go to menu „Window“ and check „Control“ or „Reset Panels“.