First, Following the URL below, I created a Viz that references Excel files on a network drive with Tableau Desktop 2019.2 and published to Tableau Server 2019.2.
That Viz was displayed correctly on the Tableau Server and changes in the Excel file on the network drive were reflected in Viz.
Next, I upgraded Tableau Server from 2019.2 to 2019.3.
Then "Unable to connect to the data source." error appeared and Viz can no longer be displayed.
Upgraded Tableau Desktop from 2019.2 to 2019.3,
I republished the Viz again, but the situation remained the same.
Since there is no problem if I checked the "Include External Files" checkbox when I publish,
There seems to be a problem with accessing from the Tableau Server to Excel files on the network drive.
Do I need any settings?
Check the Tableau Server 2019.3 "run as" user to make sure that user has network file share access to your Excel files. It's possible that user got changed when you upgraded to 2019.3. Or your network admins changed network privileges for that user. To check, you need TSM access. TSM > GUI > Configuration > Security.
