Please try the following steps on Tableau Server,
1. Open the workbook, and click the "Data Sources" tab,
2. For each of your database connection, click "Edit Connection" and check,
a. if "Embedded password in connection" is selected
b. click "Test Connection" to verify the setting, if failed, re-enter the password and try again
and then click "Save".
Afterwards, try to view the workbook again to check the results.