simplehidden instead dynamicselect

Hi,

I would like to use your plug-in, but I got troubles and I am not sure, what can be a problem:
If I push button “Dynamic Select Field” in form editor, I get this:
[simplehidden dynamicselect-264 “cf7_dynamic_select_do_example1”]
…on front is generated only this text and I am not sure, what is a problem.

…if I change simplehidden to dynamicselect, that render empty space.
I am testing with your example in function.php

Thanks for any help

Peter

https://wordpress.org/plugins/contact-form-7-dynamic-select-extension/