Need help creating a Dynamics Business Central S2S connection

I am looking for help creating a S2S connection to MS Dynamics Business Central. Unfortunately the Celigo doc doesn't cover any of the details. I have done all of the steps that I find when I do a Google and/or Claude search, but I keep getting the error below.

Your test was not successful. Check your information and try again{"error":{"code":"Authentication_InvalidCredentials","message":"The server has rejected the client credentials. CorrelationId: 7eaa671b-f454-4cd5-8323-6183dcd39eee."}}

Anyone have any tips?