Looks like it is a user permissions issue. This is the code which is breaking –
if (!current_user_can('edit_pages') && !current_user_can('edit_posts'))
wp_die(__("You are not allowed to be here", 'mo_theme'));
You can create a new user with admin rights and check if the issue is reproducible. If you need my help, pls provide a temp wordpress login to debug this issue. Thanks