I have received a Verify Check API response code 17 (A wrong code was provided too many times). How many (exactly) is 'too many' ?
A single Verify request can be checked up to 3 times using the Verify Check API call *unless a new PIN code is generated. If you check a request more than 3 times, it will be set to FAILED and you'll not be able to check it any more (even if you get the right PIN in the end).
We do this to prevent abuse and as part of safeguarding the security the Nexmo Verify service for all our customers.
*NOTE: If a new PIN code is generated on the retry based on "pin_expiry" setting, there will be 3 more attempts available.