The error “No OAuth2 refresh token” usually occurs when the **Refresh Token** or the **Service Endpoint** URL provided are invalid.
In such scenarios, I would do the following checks ,
* Ensure the **Service Endpoint** URL provided in the Data Source Configuration is valid.
* Make sure that the steps mentioned in the Knowledge Base article [How to connect Denodo to Sharepoint Online using OData with OAuth authentication](https://community.denodo.com/kb/en/view/document/How%20to%20connect%20Denodo%20to%20Sharepoint%20Online%20using%20OData%20with%20OAuth%20authentication?category=Security) are followed correctly.
* Change the [log level](https://community.denodo.com/kb/en/view/document/Using%20logcontroller%20and%20useful%20log%20categories) to “**Trace**” and analyze the root cause, by checking the **vdp.log** file in “<DENODO_HOME>/logs/vdp” directory.
For more detailed information,you could refer to the Knowledge Base article [Microsoft SharePoint as data source](https://community.denodo.com/kb/en/view/document/Microsoft%20SharePoint%20as%20data%20source).
Hope this helps!