Form won't redirect

My form is not redirecting. This is the shortcode:

[fu-upload-form success_page="http://oururl.com/" form_layout="post_image" post_type="guest-photos" title="Upload Images"]
[input type="text" name="post_title" id="title" class="required" description="Title"]
[input type="file" name="photo" id="ug_photo" class="required" description="Your Photo"]
[input type="submit" class="btn" value="Submit"]
[/fu-upload-form]

https://wordpress.org/plugins/frontend-uploader/