Users Unable To Sign In With Bad Request Error 400

Issue

After adding a few new nodes, users are unable to sign in to Tableau Server with the following error:

Sign in failed.

Vizportal logs show 400 Bad Request error.

Environment

Tableau Server
Windows Server 2016

Resolution

Check the computer names of the server nodes and rename the computer with a name that does not have an underscore character.

Note - if nodes with underscore characters have been added to the cluster they must be removed before renaming. They can then be added back to the cluster after the new name is configured.

Cause

Computer host names contain underscore character.

Additional Information

Per RFC 952, computer hostname should not include underscore character.

A "name" (Net, Host, Gateway, or Domain name) is a text string up to 24 characters drawn from the alphabet (A-Z), digits (0-9), minus sign (-), and period (.). Note that periods are only allowed when they serve to delimit components of "domain style names".
https://tools.ietf.org/html/rfc952

Internet naming convention requires names to only include alphanumeric characters, the hyphen, and a period.