Tableau Prep Cannot Connect to Tableau Cloud When Proxy is Configured

First, upgrade Tableau Prep to 2018.1.2 or a newer version. Click here for downloads of Tableau Prep: Tableau Prep Downloads and Release Notes. For more information on current releases, see Install Tableau Prep and Prep Upgrade.

Option 1

Edit the Tableau Prep shortcut to include the proxy information. 

1. If necessary, create a shortcut of Tableau Prep by right-clicking Tableau Prep.exe and selecting Create Shortcut.
2. Right-click the Tableau Prep shortcut and select Properties. 
3. Under "Target", append the following after "Tableau Prep.exe", replacing values for DproxyHost and DproxyPort with the appropriate values for your environment: 
   --java-options=-DproxySet=true;-DproxyHost=127.0.0.1;-DproxyPort=8888
   

Option 2: 

Launch Tableau Prep using the below command:
C:\Program Files\Tableau\Tableau Prep 2018.1.2\"Tableau Prep.exe" --java-options=-DproxySet=true;-DproxyHost=127.0.0.1;-DproxyPort=8888
Replace the values for proxy host and port as necessary.

Note: Option 1 is only permanent as long as you are running a particular version of Prep. If you upgrade to a new version, such as 2019.1.1, you will need to re-edit the shortcut again.

See screenshot below.