Did you set up access to the Tableau Server repository? This is where you create the password for db access for "tableau" as well as "readonly". This must be done first.
Given the error message it sounds like you do have the PostgreSQL drivers installed.
If connecting to the db from Tableau Desktop this is basically what you need to do (example from online documentation):
Notice that the port is in its own location, not with the server location.
If you are trying to connect with tabcmd or tabadmin please let us know.
Yes. I did set up the Password but still not able to login.
Please show us a screen shot of your login pop-up like what I posted. You can blank out the beginning part of the Server text box.
Also, can you show us the exact commands you used in tabadmin for creating the password (you can leave the password blank ).
Did you use any special characters (é, Ñ, etc.) or character set (Polish, French, etc.) in the password?
A few things to try:
1. Server should be "servername", not "http://servername"
2. In a distributed system, postgres might be on another host. Look in the config file at C:\ProgramData\Tableau\Tableau Server\data\tabsvc\config\workgroup.yml (or where ever you installed Tableau) for a line that says "pgsql.host:", followed by a hostname. If there is, use that hostname.
3. The port is 8060 by default, but may have been changed. Look in the config file (see above) for a line that says "pgsql0.port:", followed by a port number. If there is, use that port number.
I hope you didn't forget to
Be sure to follow Rick K.'s suggestions.