Auto fill user data in form

I’ve been through the documentation and found the tags to use to drag in website info, but for some reason its not including the user data. The page information sends fine.

This is what is included in the message body:

From: [_user_first_name] [_user_last_name] <[_user_email]>

Lesson: [_post_title]
[_post_url]

All that comes through in the email is:

From:   <>

Lesson: XXXXXXXXXXXXX

(lesson info came through fine – blocked out to not show links here)

The page is only displayed for already logged in users (its part of a membership site) and I checked that the relevant profile fields are set on the account I am using to test.

Any idea what is going wrong?
Thanks