Sometime the API for adding new contact in v2 returns
400: Bad request.
Doesn't happen all the time. Any reason why?
Is it that we are hitting our API rate limit?
Thank you for reaching out to Constant Contact's API Support.
A 400 error is not related to your rate limits; you would be receiving a 403 error if you were hitting your rate limits.
A 400 error indicates that the data being sent is not formatted correctly or is missing something. Feel free to post a code snippet of what you are submitting and we can look for the cause.