There's a new version of the HubSpot API
As of November 30, 2022, HubSpot API Keys are being deprecated and are no longer supported. Continued use of HubSpot API Keys is a security risk to your account and data. Your API Keys could be deactivated at any time after Nov. 30th, and we recommend that you migrate to Private Apps as soon as possible so you do not lose business-critical functionality.
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.