Hi Katherine,
missing-input-response means, if the webhook is sending the correct {{lead.token}} -- which it must be, if it doesn't happen in all calls -- that the hidden form field that stores the user "fingerprint" was empty when the form was submitted.
If everything else is set up correctly on the client (JS) side to populate the hidden field, then missing-input-response always means the submission was from a bot.
However... if the client side is not completely correct, then it's possible for the hidden field to not be populated for another reason. So in that case missing-input-response doesn't point directly to a bot, it could be malfunctioning JS.
Please open a new thread in Products and supply your URL and the Activity Log entry/detail.