Custom field value not appearing

Hi there. This plugin looks perfect but I can’t seem to get it working. I need to retrieve the value of a reference number. So I added this:

[dynamictext dynamictext-388 “CF7_get_custom_field key=’reference_number'”]

However on the front end, nothing appears. The HTML code generated looks like this:

<input type=”text” name=”dynamictext-388″ value=”” class=”wpcf7-text” size=”40″>

So the value is empty. Any idea how this can be fixed?

Thanks.

https://ww.wp.xz.cn/plugins/contact-form-7-dynamic-text-extension/