INVALID OPERATION WITH EXPIRED PASSWORD error

My question: I’m authenticating to a Salesforce Sandbox environment and have used a POST request to https://test.salesforce.com/services/oauth2/token to get the auth token. I can successfully get the auth token.

I then use that auth token in a subsequent POST call to {{_instance_url}}/services/data/v{{version}}/commerce/oci/availability/availability-records/actions/get-availability.
Auth Type is “Bearer Token” and token is passed in the Authorization Header as “Bearer {{_authorization_key}}”
I then get a 401 Unauthorized with this message:

“message”: “Your password has expired. Please reset your password.”,
“errorCode”: “INVALID_OPERATION_WITH_EXPIRED_PASSWORD”

But the password is not expired. I can still log into the Salesforce instance and am able to get an auth code?