Magento 2 Integration Error

I have followed the instruction in https://knowledgebase.constantcontact.com/articles/KnowledgeBase/41006-Connect-Your-Constant-Contact-Account-with-Magento?lang=en_US

but when I try to connect, it always shows this error:

I'm using Magento 2.4.5.

Please help me with this case.

Thank you.