@Kamal Thanks for using Microsoft Q&A forum and posting your query.
Azure data factory does have a native connector for Hubspot. In Hubspot linked service you can configure below details to establish connection. Not sure what was the reason to go with REST connector when ADF has native hubspot connector. In REST connector you cannot provide Access token and refresh token from your Hubspot app. Hence recommend trying to explore ADF Hubspot connector.
You can explore more about this connector from this document: Copy data from HubSpot using Azure Data Factory or Synapse Analytics
For complete implementation steps, you can also refer to this public article by a community volunteer: Connecting to HubSpot from Azure Synapse Analytics or Azure Data Factory
Hope this info helps.
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