BBIS
This has been resolved for BBIS in BBIS 4.0 SP16 Hotfix 1615.

After initially configuring reCAPTCHA or after updating the keys, navigate to a donation form page while not logged into the site to verify that reCAPTCHA is working as expected on the form. If the reCAPTCHA challenge displays an error message on the form, verify the public and private keys are correct. 

BBNC
This has been resolved for BBNC in BBNC 7.1 SP3 Patch 3.

Also, ensure your NetCommunity username is not prepopulated into the reCapatcha Public Key field:

1. From Administration>Sites & Settings, scroll to the reCaptcha section
2. Review the Public Key field - if your username is prepopulated, remove it
3. Click Save at the top of the screen