I have been researching this and I was not able to find any evidence of errors or any failures on the API. In addition, I was able to find evidence of contacts added to your account recently through the API.
Would it be possible to provide some information about how your integration should work normally versus what is happening now? It would also be a great help if there was a method for us to test your integration to see what happens. If this information is too sensitive to share on our public forum, you can reach out to us by email at firstname.lastname@example.org