Google reCAPTCHA doesn't work – contact form deactivated

Hi there,
when I open the Contact-Page of our customer’s Website I get the message:

“Dieses Kontaktformular ist momentan deaktiviert, da Sie den Google reCAPTCHA-Service noch nicht akzeptiert haben. Dieser ist für die Validierung des Sendevorgangs jedoch notwendig”
(This contact form is currently deactivated because you have not yet accepted the Google reCAPTCHA service. However, this is necessary for the validation of the sending process.)

At WP Backend I checked site keys: “We were able to properly connect and verify your API keys with Google reCAPTCHA”

Please help, thanks a lot in advance ;-)
Marc

PS: access data as “private content”