Not able to create new page in Custom Pages Editor

I am trying to create a custom page, but when I go to Edit Custo Pages and click on Actions->New Page nothing happens.

I am not able either to drag or drop any control since no page was created.

With the javascript console the only thing I saw when I enter on the “Edit Custom Pages” page is the following:
J_ALTUI_uimgr.js:7008 Uncaught TypeError: Cannot read property ‘name’ of null(anonymous function) @ J_ALTUI_uimgr.js:7008each @ jquery.min.js:2_updateDynamicDisplayTools @ J_ALTUI_uimgr.js:7005_displayPages @ J_ALTUI_uimgr.js:10886pageEditPages @ J_ALTUI_uimgr.js:10983dispatch @ jquery.min.js:3r.handle @ jquery.min.js:3

Any advice on what I might be doing wrong?

Thank you very much.

What version appear in the footer ?