Checkbox Validation message not working.

Hi, I’m trying to create this contact form with GDPR agreement.

However, when creating a checkbox or using the ‘acceptance’ option I dont get any messages if not checked.

It doesn’t send the message if not checked, so that works. But I would like to let people know that they need to check this specific box in order to get the message sent..

Neither setting it at Required, or doing it with jquery has worked out for me..

Any ideas? Thanks