That's a known bug in 1.7.1 version - AJAX calls does not work when site is installed in subfolder. We have fixed it in upcoming 1.7.2 version that will be released soon. For now I have installed 1.7.2-dev version with the fix.
Please try to create completely new competition and test on it. I presume DEMO competitions can have some issues as we did not update demo data for some time. We have plans to completely update it in 1.8 version.
Also strange that it has blank space there. May be field is generated, but hided due to some conflicts with template's CSS?
Can you try to use English interface? May the problem is in IT translation file (we had such issues with FR language files).
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