You need to configure the database connection for live writebacks and sync.
Start by clicking Configure source and then Ok in the confirmation pop-up to go to the workspace.
Configure source
Note that the source is mentioned as 'NA' in the status bar since it is yet to be configured.
Choose the data source from which the data was fetched using DirectQuery (this is because the source and destination tables are the same). Click Continue.
Choose the source
Enter the source details and save it by clicking Save Source.
Enter source details and Save
You'll see a success message after the source table is configured.