Merren Theme - Megamenu Module Doesn't Work Properly?

[likwid]

I write about my problem on forum, beacause neutronthem, developer of merren theme, doesn't reply on my emails. I can't create menu with sub menu in megamenu module, because all the time "An error occurred." has shown when I try add category block or add product block. Even when I tried modified existing example menu problem occurred. My prestashop version is 1.6.1.4 and I don't use any extra modules. I also tested on fresh Prestashop 1.6.1.0 and problem exist as well. Version of nt megamenu module is v2.0.6. Example steps I do to create menu:

1. Add main menu - Settings: main menu (select an option or fill out...), name (name), display (Main menu), submenu type (mega), position (1), rest options are left default.

2. Add 2 columns with width 3/12 and positions 1 and 2.

3. In column I can add: category block, product block, brand block, custom link, custom content. When I try to add category or product block and save then show "An error occurred" alert and nothing is change. When I try to add custom link or custom content then it shown as main menu but not as submenu as it should.

 

I tried different combinations of setting and always same.

 

If anybody had same problem and know how to resolve it please reply.