Good Morning Luis,
Have you recently upgraded to Tableau Desktop 9.3 from a previous version? Were you using the Sync Client in the previous version?
If so, you might experience this error until you disconnect the Sync Client from Tableau Online and reconnect. That is if the connection from the old version persists you might experience issues. Disconnect the Sync client and reconnect.
If this corrects the issue, please note this response as 'helpful' and or the correct answer.
Tableau Online Deployment Advisor
No, it's a new installation with Tableau 9.3. This machine never had previously Tableau installed.
Then, I'd recommend opening a support ticket. There will be some hands-on diagnosis that will need to be conducted.
One other possibility is that your Online account is using Single Sign-on (SSO). In my organization, in order to use the Sync client, I had to have a non-SSO Tableau Online account.