First and last name not registering

Hi,

I have the following fields listed in contact form 7:

<label>First name:
[text* mc4wp-Firstname] </label>

<label>Last name:
[text* mc4wp-Lastname] </label>

I have listed the following in my mailchimp audience settings:

Field label and type
Firstname with FNAME as merge tag.
Lastname with LNAME as merge tag.

When I send the registration form, it only fills in the e-mailadress. First name and last name remain empty. I’m using the integration checkbox provided by the plug-in.