Your plugin is working great in the sign up form and in CF7 - however, only in the sign up form am I able to submit marge tag values.
The relevant code in the sign up form:
<input type="hidden" name="ORIGIN" value="sidebar" />
[text mc4wp-ORIGIN class:hidden "contact"]
Can you see any errors? The CF7 form fails silently, and there is no error notification. When the ORIGIN field is required (in MC settings), then no confirmation email is sent to the user at all. When not required, user may confirm but the field is blank.