Clicking on Add slide – nothing happens

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The issue can be found here: http://www.architectmb.host56.com/
The preview works: No
It works with other themes: No
It works when I disable all other plugins: No
Meta Slider version: 3.3
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Dear Support,

When I’m clicking in meta slider “Add slide”, nothing happens. No pop up window… Actually when I want to upload a new theme, in WP dashboard, clicking to “Upload Theme”, also nothing happens, no pop up window… But if I want to upload a new plugin, the window pops up, and it works properly.
I’ve tried these in 3 different computers, 3 different internet browsers, but same problem in each case.
Please help me to solve the problem!

Thank you in advance,

zsotto

https://wordpress.org/plugins/ml-slider/