I'm getting an error that a contact already exists in Constant Contact, but I know it's not in that list.
Constant Contact identifies duplicates at the account level so you may see this error even if the contact is in another list. If you'd like to move that contact to a different list in your Constant Contact account, you can update the contact instead of creating it. To do so, you use the following workflow:
Add a Find Contact action to search for the email address. Make sure to select the option to create a new contact if none is found.
Replace the Create Contact action with the Update Contact action and set it up. This will allow the Zap to update the list the email belongs to, whenever it's already been added to your account.
I'm getting an error saying "You don't have permission to perform this action"
Constant Contact requires your account to have the Account Manager role in order to be able to add or edit Contacts via their API. Learn more here by looking at the Constant Contact help guide for this setting.