There's a new version of the HubSpot API
As of November 30, 2022, HubSpot API keys are no longer a supported authentication method for accessing HubSpot APIs. Instead, you should use a private app access token or OAuth to authenticate API calls. Learn more about this change and how to migrate an API key integration to use a private app instead.
HubSpot has a few limits in place regarding merged contact records and form submissions for contact records:
If you find that you're exceeding either of these limits because of testing, we'd recommend deleting the test contacts, and creating a new test record. Using the same email address in the new contact would not restore the originally deleted contact, and any form submissions with the email would be associated to the new record and not the deleted record.