reCAPTCHA

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Fill out the form similar to the screenshot below.  The label should be a description you recognize. 
For the type, make sure to choose V2 and "I'm not a robot".  In the domains section, make sure to specify your domain name.:

After submitting the form, the next screen will present you with the site key and secret key.

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1. Your theme must support reCAPTCHA.  The earliest theme supporting reCAPTCHA was Mr. Teas on 5/16/2016.  Some themes are still awaiting the updated code.

2. There is a flag that was primarily used for legacy sites to show/hide reCAPTCHA and can still affect the StoreFronts.  Make sure that checkbox is checked. 

   Panel
   You can view this setting by going to Advanced → Affiliate Management → Settings → Require Captcha