Do you mean by "the information doesn't go back to the lead" that the form is not pre-filled with the person's field values? As Sanford tried to clarify three years ago? 😉
If so, check if the link in your email does have the mkt_tok URL parameter on it. This is nothing you do, this is a Marketo system setting. And it's the expected behavior that this parameter vanishes after a split second or so. That is a change that Marketo introduced mid 2019. Also, if you test this with your own email address on your own computer you might already have cookies written that could disturb the process. Better clear cookies first.
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