sharepoint enterprise – "Unexpected HTML Document Received HTML Document" with CMIS Workbench

I have configured CMIS in a few SharePoint sub-sites.

When I access a particular site, CMIS Workbench generates an error:

Unexpected document received: HTML document

I have another subsite (in the same site collection) that works perfectly with CMIS Workbench.

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Note: The CMIS feature (Site Features) and Basic Authentication (Web Application) are enabled.