I'm getting "incorrect CAPTCHA" error message trying to submit the account registration form.
This error message is related to the default Magento or third-party captcha. When you use a custom theme, it hides "I'm not a robot" checkbox and it's not available for submitting. Therefore, ''Incorrect CAPTCHA'' message is displayed.
The solution is pretty easy: just disable the default Magento 2 captcha or third-party captcha in the admin. The ''Incorrect CAPTCHA'' message should be gone. If it still appears, please do not hesitate to create a support ticket.
If your CAPTCHA is not accepted, the problem may not be that you are reading or typing, perhaps something happened with the code.
One of the possible solutions, when you see an incorrect captcha message in Magento 2, is to make captcha 1 -> 0 in core_config_data table. Try after clearing cache and if not work then reindex.
Update below row in database:
Update core_config_data set value=0 WHERE path LIKE '%admin/captcha/enable%'
php bin/magento cache:flush
php bin/magento cache:clean
If you do not have this line, you have to insert it.
It can help to solve the admin incorrect captcha in Magento 2.
If these steps did not help you solve the problem or you still have any questions, then feel free to contact our support service. We will help you to fix the problem with incorrect captcha when login as an admin in Magento 2.
See more details on Google Invisible reCaptcha page