I am trying to set up an automation for the following:
Google Sheets to ActiveCampaign
Every a new subscriber is added to the sheet, I want this subsciber to be added to a list in AC
The error message returned is:
The app returned "No Result found for Subscriber with id 7 (404)".
What I am struggling with is setting up the AC side (see image attached). It is not clear whether I should specify the Contact ID or email address, and it seems that Zap doesnt; read out the last row email address
Hi there
Welcome to the Community! 
I looked at the screenshot, and it seems like you've currently added the ID collected from Google Sheets on the Contact ID field, when the field is expecting an ActiveCampaign ID of the contact.
Since the step looks for a contact based on both the parameters, the ActiveCampaign ID of the contact and the email address, and as an incorrect value is mapped as the Contact ID, the step is failing.
I'd recommend you to empty the Contact ID field and search only on the basis of Email as we only require one of the fields for the step to search for a contact and subscribe them to a List.
In addition, I wanted to let you know that if a contact doesn't already exist with the same email address from your trigger step, the current action may not work as expected. If you're uncertain whether all the email addresses from your trigger step are present in your ActiveCampaign account, I recommend including a "Create or Update Contact in ActiveCampaign" action step before the "Subscribe or Unsubscribe Contact From List" action. This will ensure that the necessary contacts are created or updated before proceeding with the subscription or unsubscription process.
Hopefully, this helps! 
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