I can not select a form with the select field Cleverreach Formular

Install CleverReach: ok
Insert CleverReach API Key: ok, my CleverReach Groups are shown
Form > Builder > Select Field “CleverReach Formular”: The select field is there and its content are my groups:
HTML Code of this select field:

<select name="haet_cleverreach_get_fields">
                                							<optgroup label="Liste: Architekten Österreich">
									</optgroup>
							<optgroup label="Liste: Architekten Deutschland">
									</optgroup>
							<optgroup label="Liste: Architekten Italien">
									</optgroup>
							<optgroup label="Liste: Architekten Südtirol">
									</optgroup>
							<optgroup label="Liste: Ueber-Website-angemeldet">
									</optgroup>
					                            </select>

However, I cannot select a group. When I hover with the mouse over a group in the select field nothing happens. Also when I click on a group in the select field nothing happens. Also with keyboard, I cannot select a group with the select field CleverReach Formular

In the Firebug Konsole there are no errors.
Version CleverReach: Version 1.5
Wordpress 4.5.2, local Installation on xampp

What could be?

https://wordpress.org/plugins/cleverreach/