Why do I get authentication errors for ALM/QC when I've correctly entered my credentials?

If you are running ALM/QC on WebLogic or WebSphere, there could be a problem with the server configuration that will interfere with your ability to connect with Hub. Basic Authentication is enabled by default in WebLogic and WebSphere and intercepts the REST API authentication requests there and needs to be switched off for the application domain. For WebLogic this is done by inserting this parameter:

<enforce-valid-basic-auth-credentials>false</enforce-valid-basic-auth-credentials>

within this section

<security-configuration></security-configuration>

...of the config.xml of the domain that ALM is configured on.