TokenException for Historical API

I've been successfully retrieving data from various API endpoints such as "". However, I'm encountering an error with the endpoint "". Despite using identical headers, including the "Authorization : token api_key:Enqxxxxxxxxxxx", I receive the following error:

"status": "error",
"message": "Incorrect `api_key` or `access_token`.",
"data": null,
"error_type": "TokenException"
I have a subscription to the Historical API and would appreciate any assistance in resolving this issue.
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